Download 1 Unit 2: Atomic Theory Unit Notes Name: Period: ______

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Period: _______
Unit 2: Atomic Theory Unit Notes
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Unit Objectives:
Understand that the modern model of the atom has evolved over a long period of time through the work of many
scientists
Discuss the evolution of the atomic model
Relate experimental evidence to models of the atom
Identify the subatomic particles of an atom (electron, proton, and neutron)
Know the properties (mass, location, and charge) of subatomic particles
Determine the number of protons, electrons, and neutrons in a neutral atom and an ion
Calculate the mass number and average atomic weight of an atom
Differentiate between an anion and a cation
Give brief description of Gold Foil experiment and state conclusions
Distinguish between ground and excited state electron configurations
Identify and define isotopes
Write electron configurations
Generate Bohr diagrams
Differentiate between kernel and valence electrons
Draw Lewis Dot Diagrams for an element or an ion
Focus Questions for the Unit:
 What is the structure of an atom?
 How did the model of the atom change over time?
 How does the structure of an atom relate to chemical properties of elements?
YOU SHOULD BE ABLE TO ANSWER THESE IN DETAIL BY THE END OF THE UNIT
Define the following vocabulary:
Allotrope
Atom
Atomic Mass unit (a.m.u.)
Bohr model
Compound
Electron Configuration
Excited state
Ion
Lewis Dot Diagram
Neutron
Anion
Atomic Mass
Atomic number
Cation
Electron
Element
Ground state
Isotope
Mass number
Nuclear Charge
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The bold, underlined words are important vocabulary words that you should be able to define
and use properly in explanations. This is a study guide for what you will be tested on throughout
the year. The objectives are divided into categories of “Knowledge” (what you have to know) and
“Application” (what you have to be able to do).
1.) ATOMIC CONCEPTS
Knowledge
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1.
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2.
o
o
3.
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4.
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o
5.
o
Application
o Explain what happened during the
gold-foil experiment and what it
Atoms are the basic unit (building
showed.
block) of matter.
Gold foil was bombarded (hit) with
Atoms of the same kind are called
positively charged alpha particles. Most
elements.
alpha particles passed through the gold foil,
The modern model of the atom has
but some were deflected. This showed that:
developed over a long period of time
1. the atom is mostly empty space
through the work of many scientists.
2. the nucleus is small, positively charged,
and
located in the center of the atom
The three subatomic particles that make up an atom are protons, neutrons, and
electrons.
The proton is positively charged, the neutron has no charge, and the electron is
negatively charged.
(This is also referenced on Table O. Check it out!)
Each atom has a nucleus with an
overall positive charge, made up of
o Determine the nuclear charge of an
protons and neutrons.
atom. (equal to the number of
The nucleus is surrounded by negatively
protons in the nucleus)
charged electrons.
Atoms are electrically neutral, which
o Determine the number of protons or
means that they have no charge (#
electrons in an atom or ion when
protons = # electrons)
given one of these values. (Periodic
Ions are atoms that have either lost or
Table)
gained electrons and are either positively
o Compare the atomic radius and
or negatively charged
ionic radius of any given element
When an atom gains one or more
Ex: A chloride ion has a larger radius
electrons, it becomes a negative ion and
than a chlorine atom because the ion has an
its radius increases.
extra electron. A sodium ion has a
When an atom loses one or more
smaller radius than a sodium atom because
electrons, it becomes a positive ion and
the ion has lost an electron.
its radius decreases.
The mass of each proton and each
neutron is approximately equal to one
o Calculate the mass of an atom given
atomic mass unit (AMU).
the number of protons and neutrons
An electron is much less massive (has
o Calculate the number of neutrons or
almost no mass) compared to a proton
protons, given the other value
or neutron.
2
o In the modern model of the atom, the WAVE-MECHANICAL MODEL
(electron cloud), the electrons are in orbitals (clouds), which are defined as
regions of most probable electron location.
o Each electron in an atom has a specific amount of energy.
7. o Electrons closest to the nucleus have the lowest energy. As an electron moves away
from the nucleus, it has higher energy.
o Electron configurations show how
many electrons are in each orbital.
o When all of an atom’s electrons are in
the orbitals closest to the nucleus, the
o Distinguish between ground state
electrons are in their lowest possible
and excited state electron
8.
energy states. This is called the ground
configurations. (Be careful to keep
state.
the same number of electrons when
o When an electron in an atom gains a
writing the excited state.)
specific amount of energy, the electron
is at a higher energy state (excited
state)
o When an electron returns from a higher
energy (excited) state to a lower energy
(ground) state, a specific amount of
o Identify an element by comparing its
energy is emitted. This emitted energy
bright-line spectrum to given spectra
9.
can be used to identify an element.
o The flame test is an example of the
bright-line spectrum visible to the
naked eye. The color can determine the
identity of a positive ion in a compound.
o The outermost electrons in an atom are o Draw a Lewis electron-dot structure
called the valence electrons. In
of an atom.
10.
general, the number of valence electrons o Distinguish between valence and
affects the chemical properties of an
non-valence electrons, given an
element.
electron configuration
o Atoms of an element that contain the
o Calculate the number of neutrons in
same number of protons but a different
11.
an isotope of an element given the
number of neutrons are called isotopes
isotope’s mass
of that element.
o Given an atomic mass, determine
the most abundant
o The average atomic mass of an
isotope
element is the weighted average of the
12.
o Calculate the atomic mass of an
masses of its naturally occurring
element, given the masses and
isotopes.
abundance of naturally occurring
isotopes
6.
Goal setting: Based upon your learning style results and the information above list at least two
techniques you plan to use to study during this unit.
1.
2.
What grade would you like to achieve on this unit based on your efforts? _______%
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Lesson 1: Concept of an Atom
Objective: To compare and contrast the development of the models of the atom.
Often in science, we are only aware of a certain amount of information at a time. As we learn new facts, we can edit our
current knowledge and develop deeper understandings of what we are studying. This is why science is often changing...
we are constantly learning new things!
We learned in Unit 1B that the smallest unit of matter is called an element.
The concept of an atom
Atomic models are theories that describe what the physical properties of an atom are (how it looks structurally). These
physical properties will help determine the chemical proper ties of an atom (how it behaves). Our current model of the
atom, the electron cloud model, is based on all the ones that came before it.
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Please watch the following video: Structure of an Atom
The Atom – Background & History
Atom:
It is the basic building block of matter;
1. Democritus = (450 BC) Greek man who tried to answer the question about the divisibility of matter;
2. Dalton (1803)
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Known as the founder of the atomic theory
Dalton invented the word atom as the basic unit of matter which were
He also discovered that atoms of different elements have different properties and masses
Found that combining atoms of different elements formed compounds
Theory referred to as the cannonball theory because it looked like a simple sphere with uniform
density.
3. J.J. Thomson (1897)
View the following link : Cathode ray tube
You can find this on my website!
o While using a cathode ray tube he discovered that the ray was deflected (due to a magnetic/electrical field)
o
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4. Ernst Rutherford (1909)
Simulation: http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf
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o Two conclusions were therefore made:
o
1)
2)
5. Neils Bohr (1913)
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6. Wave-Mechanical/Cloud Model (Modern, present-day model)
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Developed after the famous discovery that energy is made up of both waves and particles
Still the same dense positively nucleus
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Many scientist have contributed to this theory
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LAB: Ernest Rutherford’s 1911 Gold Foil Experiment (Simulation)
PURPOSE: The purpose of this activity is to simulate Rutherford’s famous Gold Foil Experiment to
demonstrate how information can be gained about something that cannot be seen or directly measured.
MATERIALS:
7 marbles
1 meter stick
masking tape
2 rulers
PROCEDURE:
1.
2.
3.
4.
5.
Divide into 3 students per group.
Use masking tape to make a line (in the hallway or in the classroom) on the floor that is 60 cm long.
Make marks on the tape at the 5cm, 15cm, 25cm, 35cm, 45cm, and 55cm.
Place one marble on each “mark”.
Measure 1 meter perpendicularly from the center of the tape (with “marks”). Mark this spot with a small
piece of tape.
6. Place the seventh marble on this spot.
60 cm tape
1 meter
Target marbles
on 60 cm tape
“alpha” marble
on tape “spot”
7. One team member, while sitting on the floor, facing away from tape and target marbles will roll the
“alpha” marble (the marble representing the alpha particle) toward the center of the tape. This will be
repeated for 50 trials for each team member. You try to be as “consistent” (minimum variations) as
possible.
8. A second team member will record whether or not each trial is a “hit” or a “miss” A trial will count as a
“hit” or “miss” only if the “alpha” marble passes over the 60 cm tape. If the target marble is moved,
even slightly, the trial is registered as a “hit”. If the target is not moved the trial is a “miss”.
9. The third team member replaces the target marbles and returns the “alpha” marble to the team member
rolling at the time.
10. Team members switch positions after each 50 trials.
11. Record all 150 trials.
12. Measure the diameter of one of the target marbles on the 60 cm tape. Place all 7 marbles next to the
calibrated edge of the meter stick. Divide the measurement of the 7 marbles by seven to obtain the
“average” diameter of the target marble.
13. Complete recording all data collection and calculations.
14. Prepare for Rutherford Lab Quiz using similar, but not identical SAMPLE DATA.
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NAME: ____________________________
BOCK: ______ DATE: ________________
CALCULATIONS
1. Calculate the diameter of the spheres using the following formula:
Diameter =
field width X number of hits
2 X number of target marbles X number of trials
Field width =
Tot. Hits =
# Target Marbles =
# Trials =
Calculations
Calculated diameter value
2. Calculate the percent error using the following equation:
| measured value – calculated value |
% Error =
X 100
measured value
Measured value =
Calculated value =
CALCULATIONS:
% Error =
DISCUSSION
What would happen if the target marbles were smaller or larger?
Assuming your procedure is consistent, would a greater number of
trials increase your precision?
1. On what does the hit/miss ratio depend?
2. How does the number of trials affect the results?
3. Would one million trials cause the calculated diameter to be
significantly closer to the measured value than the 150 trials? In
other words, if Rutherford’s experiment were repeated today, a
thousand times would the results be different? Explain.
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Stu 1
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Hit
Classwork 2-1: Concept of an Atom
Objective: To compare and contrast the development of the models of the atom.
1. Draw below the model of the atom proposed be the following individuals
Dalton (1800)
Thompson (1897)
Bohr (1913)
2. How did Thompson’s model differ from Dalton’s model?
3. The gold foil experiment resulted in two major discoveries which were made about the
structure of the atom. What were they?
a.
b.
4. How does the Bohr model represent electrons around the central nucleus? Why (think
of spectra)?
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Practice:
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6) Explain the current model of the atom.
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Lesson 2: Subatomic Particles
Objective: To define the parts of an atom
Please watch the following video: Bill Nye Atoms
Each subatomic particle has very unique physical properties that will in turn; affect the chemical properties of the atoms
they make up. The following reading passage will help you to better understand the structure of the atom.
Understanding Atomic Structure...
The word nucleus of the atom is just like the nucleus of the cell that you learned about in Living Environment.
One of the properties of the nucleus is that it is very dense compared to the rest of the atom. This is a qualitative
observation. To put this into quantitative terms, we say that each of the subatomic particles found in the nucleus has an
approximate relative mass of 1 amu or atomic mass unit.
The majority of the atom’s mass comes from the dense center of the atom (the nucleus). However, most of the
atom is not dense; it is made of empty space. Have you ever heard of the idea that opposites attract? This principle
comes from science. Positives and negatives attract one another and this attraction holds the atom together.
Positively charged particles
The negatively
The third type
Each of the three types of subatomic particles has a different charge so that they can all co-exist in the small
space that is the atom.
- Each type of atom has a specific number of protons.
- The word “atom” implies that the
We can use the reference table to help us with many of these symbols and definitions. Look at the key on the periodic
table.
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Symbol and Name-: In compounds notation the symbols are used. When just referring to the element itself it can be
written two ways:
C-12 (symbol and mass number)
or
12 (mass number)
C
6 (atomic number)
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Atomic Number-

Atomic Mass-
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Electrons- For a neutral atom,

Nuclear Charge =
p = nuclear charge

Nucleons =
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Subatomic
Particle
Proton
Charge
Relative Mass
Location
Neutron
Electron
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Symbol
How to Calculate
Classwork 2-2: Subatomic Particles & Their Properties
Objective: To define the parts of an atom
1. Fill in the blanks
The modern model of the atom has evolved over a long period of time through the
work of many scientists.
Each atom has a nucleus, with an overall positive charge, surrounded by one or more
negatively charged ________________. Subatomic particles contained in the nucleus include
____________________ and _____________________. The proton is positively charged,
and the neutron has no charge. The electron is __________________ charged. Protons and
electrons have equal but opposite charges. The number of protons _____________ the
number of electrons in an atom. The mass of each proton and each neutron is
approximately ________________ atomic mass unit. An electron is much _______________
massive than a proton or a neutron. The number of protons in an atom
(_________________) identifies the element.
2. Fill in the following table:
Particle
Charge
Mass
+1
1
neutron
electron
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Location
Practice:
1.) In the modern model of the atom, each atom is composed of three major subatomic
particles.
a) Name the subatomic particles contained in the nucleus of the atom.
b) State the charge associated with each type of subatomic particle contained in the
nucleus of the atom.
c) What is the net charge of the nucleus?
2.) Give the names and chemical symbols for the elements that correspond to these atomic
numbers:
a. 10
b. 18
c. 36
d. 51
3.) What is the charge on the nucleus of…
a) a Cr atom? _______
b) a Ni atom? _______
c) a sodium atom?______
4.) Which statement best describes electrons?
(1) They are positive subatomic particles and are found in the nucleus.
(2) They are positive subatomic particles and are found surrounding the nucleus.
(3) They are negative subatomic particles and are found in the nucleus.
(4) They are negative subatomic particles and are found surrounding the nucleus.
5.) The atomic number of an atom is always equal to the number of its
(1)
(2)
(3)
(4)
protons, only
neutrons, only
protons plus neutrons
protons plus electrons
6.) Which particles are found in the nucleus of an atom?
(1) electrons, only
(2) protons and electrons
(3) neutrons, only
(4) protons and neutrons
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7.) A neutral atom contains 12 neutrons and 11 electrons. The number of protons in this
atom is
(1) 1
(2) 11
(3) 12
(4) 23
8.) Which statement is true about the charges assigned to an electron and a proton?
(1) Both an electron and a proton are positive.
(2) An electron is negative and a proton is positive.
(3) An electron is positive and a proton is negative.
(4) Both an electron and a proton are negative.
9.) What is the charge of the nucleus in an atom of oxygen-17?
(1) 0
(2) -2
(3) +8
(4) +17
10. Using the definitions provided above please fill in the following chart.
Symbol
# Protons
#
Neutrons
#
Electrons
Atomic
Number
Mass
Number
Nuclear
Symbol
35
17
15
C-14
16
8
17
Cl
Lesson 3:
Subatomic Particles & Ions
Objective: To compare and contrast the subatomic particles of atoms and ions.
Atoms
Neutral atoms
A neutral sodium atom, for example, contains 11 protons and 11 electrons. By removing an electron from
this atom we get a positively charged Na+ ion that has a net charge of +1.
Atoms that gain
A neutral chlorine atom, for example, contains 17 protons and 17 electrons. By adding one more electron we
get a negatively charged Cl-ion with a net charge of -1.
The gain or loss of electrons by an atom to form negative or positive ions has an enormous impact on the
chemical and physical properties of the atom. Sodium metal, for example, which consists of neutral sodium
atoms, bursts into flame when it comes in contact with water. Neutral chlorine atoms instantly combine to form
Cl2 molecules, which are so reactive that entire communities are evacuated when trains carrying chlorine gas
derail. Positively charged Na+ and negatively charged Cl- ions are so unreactive that we can safely take them
into our bodies whenever we salt our food.
Cations are
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Classwork 2-3: Subatomic Particles & Ions
Objective: To compare and contrast the subatomic particles of atoms and ions.
1.) In terms of subatomic particles, what is the difference between an atom and an ion?
2.) How can you determine the electrical charge on an ion?
3.) When an atom becomes an ion, does the element’s nucleus change?
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Practice: For the following atoms/ions determine the number of protons, neutrons, electrons,
mass number, and nuclear charge.
ATOM or
ION?
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PROTONS
NEUTRONS
ELECTRONS
MASS
NUMBER
NUCLEAR
CHARGE
N
Cu+2
8 +3
B
17
O
F-1
206
Pb
208
Pb
Ag+1
Zn+2
Mg
S-2
Challenge:
Directions: Answer the following questions on a separate sheet of paper for extra credit. You
must answer ALL questions for credit!
1.)
2.)
3.)
4.)
Iron loses 3 electrons to form an ion, what is the electrical charge of the ion?
Oxygen gains 2 electrons to form an ion, what is the electrical charge of the ion?
What number is the Lowest Common Multiple of the numbers 3 and 2?
Iron reacts with oxygen in the air to form the electrically neutral compound, iron (III)
oxide, known as rust. How many of each type of ion would be needed to form an
electrically neutral compound?
5.) Write the chemical formula for iron (III) oxide.
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Lesson 4
Subatomic Particles & Isotopes
Objective: To differentiate between isotopic forms of atoms based on number of neutrons
Atoms are identified by the numbers of protons, neutrons, and electrons that they contain. Before you can understand
the properties of atoms, how atoms combine to form molecules, and the properties of molecules, you must be familiar
with the number of protons, neutrons, and electrons associated with atoms.
From the perspective of a chemist, the entire world is composed of atoms, and atoms are composed of protons,
neutrons, and electrons. Protons and neutrons are about 2000 times heavier than an electron. A proton has a charge of
+1, a neutron has no charge, and an electron has a charge of -1. The nucleus is very dense and very small compared to
the entire atom.
If I take a sample of air from this room and put it into a box, there may be more than one type of hydrogen
atom. Remember that in order for an atom to be hydrogen, it must have a certain number of protons (protons
determine the identity of an element). The properties of atoms are determined by the numbers of protons, neutrons,
and electrons that they contain. Atoms with the same number of protons but different number of neutrons are called
isotopes of an element.
In Earth Science, you learned about Isobars. Isobars are lines (like the ones shown below) that represent areas of the
same pressure.
“Iso-” is a prefix that means same
“-tope” sounds like “type”...
The isotopic notation for an atom includes the following information: symbol of the element, the element’s
atomic number (Z) which specifies the number of protons in the nucleus, and the mass number (A) which indicates the
number of protons plus neutrons in the nucleus. [The number of electrons in a neutral atom is equal to the number of
protons in the nucleus of the atom. The mass contributed by the electrons in an atom is very small, so it is not included
when calculating the mass number.]
Atomic Symbol Notation
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ISOTOPES AND MASS
Isotope =
Example: Isotopes of Carbon (C-12, C-13, & C-14)
12
6
14
13
C
6
C
C
6
So why does Carbon have a mass of 12.011 on the Reference Table?
(there exist three different isotopes of carbon in the atmosphere – as seen just above)
Atomic Mass = the weighted average of an element’s naturally occurring isotopes
22
23.99
24.99
25.99
X
X
X
.7899 =
.1000 =
.1101 =
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Practice:
1. Use a periodic table to fill in the missing information in the following table.
Which elements listed in the table are isotopes?
2. A mystery element occurs in nature as two isotopes. Isotope A has a mass of 10.0130 amu
and its abundance is 19.9%; Isotope B has a mass of 11.0093 amu and its abundance is 80.1%.
From this data, calculate the atomic mass of the element and show all work. Lastly, identify
the element using your Periodic Table.
24
Classwork 2-4: Subatomic Particles & Isotopes
Objective: To differentiate between isotopic forms of atoms based on number of neutrons
1. What information is provided by the atomic number?
2. What information is provided by the mass number?
3. Calculate the atomic mass of copper using the data below. SHOW ALL WORK.
Element
copper-63
copper-65
Mass
62.9396 amu
64.9278 amu
Percent Abundance
69.17%
30.83%
35
37
35
37
4. Describe the similarities between 17 Cl and 17 Cl .
5. Describe the differences between 17 Cl and 17 Cl .
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Lab Activity - BUILD AN ATOM
Objectives:
1. Make atom models that show stable atoms or ions.
2. Use given information about subatomic particles to:
a. Identify an element and its position on the periodic table
b. Draw models of atoms
c. Determine if the model is for a neutral atom or an ion.
3. Predict how addition or subtraction of a proton, neutron, or electron will
change the element, the charge, and the mass of an atom or ion.
Procedure:
1. Direct your web browser to the PHET Build-an-atom simulation at:
http://phet.colorado.edu/en/simulation/build-an-atom
-
Make sure the four choices on the right of the screen (Element, Symbol, Mass Number, Charge)
are all expanded. The green + box will expand the selection, and the red – box will collapse the
section.
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Under “Model”, select the radio button that says “orbits”.
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Make sure the 3 choices at the bottom (Show element name, Show neutral/ion, Show
stable/unstable) are all checked.
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Note that at any time you can click the “Reset All” button in the bottom right corner.
Data/Results:
2. Explore the simulation.
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Which particles are you able to drag into the center? ________________________________
-
What is the center called? _________________________
3. Notice that as you build your atom, the name of the element will appear in the center, and the
element symbol will be highlighted on the “element” section in the top right.
-
What determines the name of the element you build? ____________________
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4. Notice that as you build your atom, the word “stable” or “unstable” will appear in the center.
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Identify 1 example of a stable atom and 1 example of an unstable atom in the table:
STABLE
How many protons
are in your atom?
How many neutrons
are in your atom
What is the name of the
element you built?
UNSTABLE
-
What seems to be a good rule to make the center of the atom stable? _____________________
______________________________________________________________________________
5. Notice that as you build your atom, you will see a red “+ Ion”, black “Neutral Atom” or blue “-Ion”
appear in the top right. The charge is also indicated in the “net charge” section in the bottom right.
The mass of the atom is indicated in the “Mass number” section on the right. In the table below,
check the columns that would change as a result of adding or removing the stated particle.
Name of Element
Charge
Mass
Adding/removing proton
Adding/removing neutron
Adding/removing electron
-
What is a rule for making an atom with no charge (a neutral atom)?
___________________________________________________________________
-
What is a rule for making an atom with a positive charge (a positive ion)?
___________________________________________________________________
-
What is a rule for making an atom with a negative charge (a negative ion)?
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-
Identify 1 example each of a neutral atom, positive ion, and negative ion in the table:
NEUTRAL ATOM
What is in your
atom/ion?
# protons:
Draw your atom/ion
What is the charge?
# neutrons:
# electrons:
POSITIVE ION
# protons:
# neutrons:
# electrons:
NEGATIVE ION
# protons:
# neutrons:
# electrons:
-
What is a rule for determining mass?
___________________________________________________________________
6. Design a positive ion with a charge of +2
Design a neutral stable atom with a mass
and draw your atom in the box.
of 9 and draw your atom in the box.
# protons: _____
# neutrons: _____
# electrons: _____
Element name: __________________
Mass of ion: ____________________
# protons: _____
# neutrons: _____
# electrons: _____
Element name: __________________
Charge of ion: ____________________
7. What can you make with 4 protons and 4 neutrons? ___________
A. Oxygen atom
D. Beryllium atom
B. Oxygen ion
E. Beryllium ion
C. Choices A & B
F. Choices D & E
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8. If you have 5 protons and 6 neutrons, how many electrons would you have to add to make a
neutral atom? _________
9. What is the mass of an atom with 8 protons 9 neutrons and 8 electrons? ____________
10. If you have 5 protons, 6 neutrons, & 5 electrons, what would the element symbol look like?
11. If you have 8 protons, 9 neutrons, 10 electrons, what would the charge be? ______
A. Zero, it’s an atom
D. -1 ion
B. +2 ion
E. -2 ion
C. +1 ion
Conclusion: Reflect on your findings specifically discussing how you met the stated objectives.
29
Lab Activity: Beanium Isotopes
Background
The only research chemist at Anywhere High School has discovered a new element! This element was
discovered in the mixture that makes up the baked beans in the cafeteria. The researchers have
named this element Beanium. No tests have been done on this element because the researchers could
not determine the atomic mass of this new ground breaking element.
There is a large sample of this new element in the lab at the research facility at the high school.
A reporter has learned that this top secret facility is funded from the same people that fund AREA 51.
As you may know, this secret funding comes from the international alien cover-up conspiracy started in
Roswell, New Mexico in 1947.
This lowly research chemist has brought this new element to your classroom so that the lab
technicians can determine the atomic mass of Beanium.
Materials
•
•
100-mL beaker
Sample of Beanium
Procedure
The different isotopes of Beanium are shaped like different types of beans.
1. Sort the Beanium sample into the different isotopes. Record the number of each isotope in the data
table provided.
2. Find the mass of each isotope. This is not the mass of one atom, it is the mass of all the atoms of
that particular isotope. Record these masses in the data table.
3. Follow the directions in the data table, and use your vast knowledge of average atomic masses to
find the atomic mass of Beanium.
Results/Observations
Beanium Data Table: Use only the three isotopes with the greatest number of atoms are to be
recorded. (Any others are impurities)
Isotope #1
Isotope #2
# of atoms
Total number of atoms in your sample________________
(add up the # of atoms of all 3 isotopes)
30
Isotope #3
Percent
Abundance
(# atoms / total
atoms)
(rounded to nearest
.01)
Mass of
Sample
Mass of
one atom
(mass of sample/ # of
atoms)
(rounded to nearest
.01)
Calculations
To find the atomic mass of Beanium, use the mass of one atom of each isotope as the mass number
and the percent of each isotope.
Show your work below:
The atomic mass of Beanium is __________________amu
31
Lesson 5: Bohr Diagrams
Objective: To represent the atom using the model defined by Bohr.
Look at the model of the atom proposed by Bohr (below). We know that the subatomic particle
that determines the identity of the atom is the proton and it is located in the nucleus. Does the
identity of an atom ever change in chemical reactions? NO! So do you think that the number of
protons ever changes in a chemical reaction? NO! Chemists might say then that the number of
protons is stable or not changing.
Nucleus
Bohr did not yet know about neutrons. These would not come until much later. Neutrons are also located in
the nucleus of the atom. Atoms of the same element may have different numbers of neutrons. These are
known as isotopes. However, once an atom has a specific number of neutrons, this number will not change.
For example, Cl-37 cannot give one of its neutrons away to become Cl-35!
Thomson had already discovered the electron.
Bohr’s major contribution
Since this subatomic particle is located on the outside of the atom, it is the subatomic particle that will
have the most impact on the properties of the atoms, because it is most likely to be impacted by other
atoms around it.
32
Drawing Bohr Models of Atoms
A=P=E
M-A=N
Step 1: Calculate the number of protons, neutrons and electrons using:
A=P=E
M-A=N
Step 2: put protons and neutrons in the nucleus, and electrons in the electron shells.
1st energy level
2nd energy level
3rd energy level
Let's Try a Couple of Examples:
Do APE MAN for Boron.
How many protons? neutrons? electrons?
Did you get 5 protons, 6 neutrons, and 5 electrons?
Did you round the mass before subtracting?
Draw Boron, putting the proper number of protons (5) and neutrons (6)
and electrons (5) in their proper places.
Do APE MAN for Sodium.
How many protons? neutrons? electrons?
Did you get 11 protons, 12 neutrons, and 11 electrons?
Did you round the mass before subtracting?
Draw Sodium, putting the proper number of protons (11) and
neutrons (12) and electrons (11) in their proper places.
33
Fluorine atom configuration 2-7
Fluoride anion configuration 2-8
34
Electron Configurations
**All electron configurations on thePeriodic Table are NEUTRAL (p + = e-)
*
SUBSTANCE
ELECTRON CONFIGURATION
Magnesium
2-8-2
Mg+2
2-8
Bromine
2-8-18-7
Br-1
2-8-18-8
Barium
2-8-18-18-8-2
*Lead
-18-32-18-4
shortcut allows you to cut out the first two orbitals to shorten the “address”
Valence Electrons:
Kernel Electrons: inner electrons (all non-valence electrons)
Example:
Sulfur 2-8-6
Nitrogen: 2-5
Principle Energy Level (n) = electron energy levels - each level can hold a maximum # of electrons
Maximum # of electrons in an energy level = 2n2 where n = quantum # (or period #)
Maximum number of electrons (2n2)
2
8
18
32
Principle Energy Level (n)
1
2
3
4
Sample question: What is the
maximum number of electrons that
can occupy the 3rd principal energy
level in any atom?
35
Classwork 2-5: Bohr Diagrams
Objective: To represent the atom using the model defined by Bohr.
1. What subatomic particle is most important in determining the properties of atoms?
Why?
2. Give the electron configurations for the following:
a. Carbon ____________
b. Strontium ____________
c. Fluorine ____________
d. Argon ____________
e. Sodium ____________
f. Lithium_____________
36
Practice: Construct Bohr diagrams for the following. Some are neutral and some are ions-Be careful
Carbon
Fluorine
Beryllium
Br
Li
Ca2+
Na+
S2-
Argon
Phosphorus
Oxygen
O2-
Aluminum
Sodium
N3-
He
37
Lesson 6: Electrons and Energy
Objective: To relate energy state to electron location
The modern or “quantum mechanical” model of the atom describes energy levels as being
further subdivided into sublevels and orbitals. The word “orbital” is one you need to know, and
simply refers to a region of space around the nucleus where there is a high probability of finding
an electron. The more electrons an atom has, the more orbitals it will use. Each orbital contains
a maximum of 2 electrons.
Each electron in an atom has a particular amount of energy depending on how close
they are to the nucleus. Electrons in orbitals that are closer to the nucleus are more
energetically stable and are at a lower energy. When all the electrons in an atom are in their
lowest possible energy levels, the atom is said to be in the “ground state.” The ground state
electron configuration is the one displayed on the periodic table below each element.
When an atom interacts with an outside energy source such as heat, light or electricity,
the electrons can be affected. The most accessible and therefore most likely to be affected
electrons are the valence electrons. If the electron can absorb just the right amount of energy
to pop it to a higher energy level, it will indeed do this. The atom is now described as being in
the “excited state.” An atom in the excited state is unstable and will immediately emit the
energy in the form of light as the electron(s) return to the ground state. The excited state
configuration of an atom has the same number of electrons as the ground state. For example,
oxygen in the ground state is 2-6, but in the excited state might be 2-5-1, or 1-7, or 1-6-1. In all
cases the total number of electrons is that of an atom of oxygen… that is 8 electrons.
Ground State =
 ground state electron configuration for Li is 2-1
Excited State =
 excited state electron configuration for Li could be 1-2, 1-1-1
So how can you tell if you have a ground state or excited state configuration?
38
Bright Line Spectrum
We need to consider the nature of light, or what is called the electromagnetic spectrum.
The electromagnetic spectrum is a continuum of all electromagnetic waves arranged according
to frequency and wavelength. The sun, earth, and other bodies radiate electromagnetic energy
of varying wavelengths. Electromagnetic energy passes through space at the speed of light in
the form of sinusoidal waves. The wavelength is the distance from wave crest to wave crest (see
figure below).
Light is a particular type of electromagnetic radiation that can be seen and sensed by the human
eye, but this energy exists at a wide range of wavelengths. The micron is the basic unit for
measuring the wavelength of electromagnetic waves. The spectrum of waves is divided into
sections based on wavelength. The shortest waves are gamma rays, which have wavelengths of
10e-6 microns or less. The longest waves are radio waves, which have wavelengths of many
kilometers. The range of visible consists of the narrow portion of the spectrum, from 0.4
microns (blue) to 0.7 microns (red).
HIGH ENERGY
LOW ENERGY
Ground à excited
Ground ß Excited
When atoms absorb energy their electrons will shift to a higher energy level or an excited
state.
39
This is a very unstable and temporary condition so the electrons will fall back down or drop to a lower
state energy level (or the ground state.)
On the left of the diagram, electrons are shown being excited from the 2nd energy level (n = 2) to
the 3rd, 4th and 5th energy levels. As they return to their original energy level (to the ground state),
they emit their extra energy in the form of a particular frequency (color) of light.
A spectrum of samples of unknown composition can be observed in order to identify the elements present.
Much of what we know about the structure and history of the universe has been figured out by observing the
spectra of stars.
This diagram shows an example of how a spectrum is taken and what it would look like.
Another Resource:
 http://www.visionlearning.com/library/module_viewer.php?mid=51&l=&c3=
(scroll down to “Bohr Atom: Quantum Behavior of Hydrogen” animation)
40
Classwork 2-6: Electrons and Energy
Objective: To relate energy state to electron location
1. What is the relationship between the distance an electron is from the nucleus, and its
energy?
2. How does an atom enter the “excited state?”
3. What does an atom in the excited state do as its electron(s) return to the ground state?
4. (T/F) ____ When an atom becomes excited it loses electrons.
5. What is a “Bright line spectrum?”
6. Why do you think that the bright line spectrum of an element can be thought of as a
“fingerprint” for that element?
7.
The diagram shows the characteristic spectral line patterns of four elements. Also shown are
spectral lines produced by an unknown substance. Which pair of elements is present in the
unknown?
1.
2.
3.
4.
lithium and sodium
sodium and hydrogen
lithium and helium
helium and hydrogen
41
Practice:
Distinguish between ground state and excited state electron configurations below:
Bohr Electron Configuration
2-1
2-0-1
1-1-1
2-7-3
2-8-2
2-8-8-2
2-8-17-6
2-8-18-8
2-6-18-1
2-5-18-32
Ground (G) or Excited (E) state?
1. Compared to a sodium atom in the ground state, a sodium atom in the excited state must
have
1.
2.
3.
4.
a greater number of electrons
a smaller number of electrons
an electron with greater energy
an electron with less energy
2. Which principal energy level change by the electron of a hydrogen atom will cause the
greatest amount of energy to be absorbed?
1.
2.
3.
4.
n = 2 to n = 4
n = 2 to n = 5
n = 4 to n = 2
n = 5 to n = 2
3. Spectral lines produced from the radiant energy emitted from excited atoms are thought to
be due to the movements of electrons
1.
2.
3.
4.
from lower to higher energy levels
from higher to lower energy levels
within their orbitals
out of the nucleus
4. What is the electron configuration of a sulfur atom in the excited state?
1.
2.
3.
4.
2–4
2–6
2–8–6
2–8–5-1
42
5. Electron X can change to a higher energy level or a lower energy level. Which statement is
true of electron X?
1.
2.
3.
4.
Electron X emits energy when it changes to a higher energy level.
Electron X absorbs energy when it changes to a higher energy level.
Electron X absorbs energy when it changes to a lower energy level.
Electron X neither emits nor absorbs energy when it changes energy level.
Choose from the following set of answers for questions 10-12:
1.
2.
3.
4.
2–7
2–8
2–8–1
2–7-1-1
6. Represents the electron configuration of an atom of sodium in the ground state. _______
7. Represents the electron configuration of the Na+1 ion. ________
8. Represents an excited state electron configuration for an atom of sodium. ________
9. The characteristic bright-line spectrum of an element is produced when its electrons
1.
2.
3.
4.
form a covalent bond
form an ionic bond
move to a higher energy state
return to a lower energy state
43
Lab Activity - Flame Tests
Purpose: To understand that substances can be identified by flame color. To
learn how we get light and colors and understand what the atom is doing to
produce that light
Safety Concerns: Be sure to wear safety goggles and heat resistant gloves
Materials:
Nichrome wire loop
water
50mL beaker
Heat resistant gloves
Copper(II) sulfate
Sodium chloride
Lithium chloride
Barium chloride
Potassium chloride
Copper chloride
Strontium chloride
Safety Glasses
Procedure:
1. Fill the 50mL beaker with water.
2. PROPERLY, light the Bunsen burner. Adjust the
burner so that the flame is only blue.
3. Dip the Nichrome wire in the water, and then
into one of the chemicals. Make sure that
some of the chemical adheres to the
Nichrome wire, if it doesn’t dip the water in
water and try again.
4. Holding the burner at a slight angle place the
wire in the flame and observe the color. Record your data in your CHART!!
Be as specific as possible about the color.
5. Move to the next lab station and repeat this procedure
6. Repeat this procedure until you’ve tested each chemical.
7. Remember to CLEAN UP!!!
Conclusion/Questions:
Data:
Compound
Copper(II) sulfate
Sodium chloride
Lithium chloride
Barium chloride
Potassium chloride
Copper chloride
Strontium chloride
Flame Color
44
What is causing the
metal-containing
compounds to emit light?
(Be sure to use the
following terms in your
answer: ground state,
excited state) Use a
diagram if necessary.
45
Emission Spectra Data
4.0
4.5
5.0
5.5
6.0
6.5
7.0
Light Source : _________________ Color of Light: _________________
4.0
4.5
5.0
5.5
6.0
6.5
7.0
Light Source : _________________ Color of Light: _________________
4.0
4.5
5.0
5.5
6.0
6.5
7.0
Light Source : _________________ Color of Light: _________________
4.0
4.5
5.0
5.5
6.0
6.5
7.0
Light Source : _________________ Color of Light: _________________
4.0
4.5
5.0
5.5
6.0
6.5
7.0
Light Source : _________________ Color of Light: _________________
4.0
4.5
5.0
5.5
6.0
6.5
7.0
Light Source : _________________ Color of Light: _________________
46
47
Lesson 7: Lewis Dot Diagrams:
Objective: To represent the atom using the model defined by Lewis
The electrons are the subatomic particle that is most important for our study of Chemistry because it is
on the outside of the atom and therefore it is the particle that is most likely to be affected by other
atoms around it. Due to this, Chemist’s use another kind of diagram to help keep track of an atoms
electrons called a Lewis Dot Diagram.
Lewis Dot Diagrams
To find the number of valence electrons, you start by writing down the electron configuration.
1.
2.
3.



8
5
1 2
X
3
6
4 7
4. If you are working with an ion you must adjust the valence electrons (add or subtract electrons) in the
configuration before constructing your Dot Diagram – be sure to draw your final diagram with the initial
charge on the ion.
An cation will always have brackets without any electrons drawn inside and its charge outside on the
top right.
A anion will always have all eight electrons drawn inside the brackets with its charge outside on the top
right.
48
Classwork 2-7: Lewis Dot Diagrams
Objective: To represent the atom using the model defined by Lewis.
1. Give the number of valence electrons for the following.
a.
b.
c.
d.
e.
f.
Carbon ____________
Strontium ____________
Fluorine ____________
Argon ____________
Sodium ____________
Lithium_____________
2. Why are the valence electrons the most important electrons?
49
Construct Lewis Dot diagrams for the following:
Carbon
Fluorine
Beryllium
Br
Li
Ca2+
Na+
S2-
Argon
Phosphorus
Oxygen
O2-
Aluminum
Sodium
N3-
He
50
Lesson 8: Article Analysis
Objective: To relate the nature of science to historical influences.
Reading: Niels Bohr and Ernst Rutherford: The Life of a Scientist.
Scientists are people too and can lead very interesting lives. Just as our childhood and
environment mold us into who we are, the life experiences of a scientist mold their character
and ability to achieve greatness. Read the attached two passages about two scientists that were
instrumental in defining the structure of the atom. Answer the following questions on a
separate piece of paper to be collected upon completion of your reading.
1.
What type of education did both scientists receive in their youth and how did it
influence their careers? Do they have anything in common?
2. The work of one scientist can very much influence the work of another scientist. How
does this statement apply to Bohr and Rutherford? Support your answer with examples
from the passage.
3. Both scientists lived and worked during Hitler’s reign. How did this influence their
ability to complete their work? Support your answer with examples from the passage.
4. If Rutherford were still alive, what do you think his reaction would be to the creation of
the atomic bomb and Bohr’s role in its creation?
51
Niels Bohr
1885 - 1962
Niels Bohr was born and educated in Copenhagen, Denmark. He
lived, worked, and died there, too. But his mark on science and
history was worldwide. His professional work and personal
convictions were part of the larger stories of the century.
At the University of Copenhagen, he studied physics and played
soccer (though not as well as his brother, who helped the 1908
Danish soccer team win an Olympic silver medal). After receiving
his doctorate in 1911, Bohr traveled to England on a study grant
and worked under J.J. Thomson, who had discovered the electron
15 years earlier.
Bohr began to work on the problem of the atom's structure.
Ernest Rutherford had recently suggested the atom had a
miniature, dense nucleus surrounded by a cloud of nearly
weightless electrons. There were a few problems with the model,
however. For example, according to classical physics, the
electrons orbiting the nucleus should lose energy until they spiral
down into the center, collapsing the atom. Bohr proposed adding
to the model the new idea of quanta put forth by Max Planck in
1901. That way, electrons existed at set levels of energy, that is,
at fixed distances from the nucleus. If the atom absorbed energy,
the electron jumped to a level further from the nucleus; if it
radiated energy, it fell to a level closer to the nucleus. His model
was a huge leap forward in making theory fit the experimental
evidence that other physicists had found over the years. A few
inaccuracies remained to be ironed out by others over the next
few years, but his essential idea was proved correct. He received
the Nobel Prize for this work in 1922, and it's what he's most
famous for. But he was only 37 at the time, and he didn't stop
there. Among other things, he put forth the theory of the nucleus
as a liquid drop, and the idea of "complementarity" -- that things
may have a dual nature (as the electron is both particle and
wave) but we can only experience one aspect at a time.
In 1912 Bohr married Margrethe Nørlund. They had six sons, one
of whom, Aage, followed his father into physics -- and into the
ranks of Nobel Prize-winners. Bohr returned to Denmark as a
professor at the University of Copenhagen, and in 1920 founded
the Institute for Theoretical Physics -- sponsored by the Carlsberg
brewery! Bohr remained director of the institute for the rest of
his life, except for his absence during World War II. Bohr's
personal warmth, good humor ("Never express yourself more
clearly than you can think," he once said), and hospitality
combined with world events to make Copenhagen a refuge for
52
many of the century's greatest physicists.
After Hitler took power in Germany, Bohr was deeply concerned
for his colleagues there, and offered a place for many escaping
Jewish scientists to live and work. He later donated his gold
Nobel medal to the Finnish war effort. In 1939 Bohr visited the
United States with the news from Lise Meitner (who had escaped
German-occupied Austria) that German scientists were working
on splitting the atom. This spurred the United States to launch
the Manhattan Project to develop the atomic bomb. Shortly after
Bohr's return home, the German army occupied Denmark. Three
years later Bohr's family fled to Sweden in a fishing boat. Then
Bohr and his son Aage left Sweden traveling in the empty bomb
rack of a British military plane. They ultimately went to the
United States, where both joined the government's team of
physicists working on atomic bomb at Los Alamos. Bohr had
qualms about the consequences of the bomb. He angered
Winston Churchill by wanting to share information with the
Soviet Union and supporting postwar arms control. Bohr went on
to organize the Atoms for Peace Conference in Geneva in 1955.
In addition to his major contributions to theoretical physics, Bohr
was an excellent administrator. The institute he headed is now
named for him, and he helped found CERN, Europe's great
particle accelerator and research station. He died at home in
1962, following a stroke.
"An expert is a man who has made all the mistakes which can be
made, in a very narrow field."
53
Ernest Rutherford
1871 - 1937
Ernest Rutherford's family emigrated from England to New Zealand before
he was born. They ran a successful farm near Nelson, where Ernest was
born. One of 12 children, he liked the hard work and open air of farming,
but was a good student and won a university scholarship. After college, he
won another scholarship to study at Cambridge University in England -- a
turning point in his life. There he met J.J. Thomson (who would soon
discover the electron), and Thomson encouraged him to study recentlydiscovered x-rays.
This was the start of a long, productive, and influential career in atomic
physics. Rutherford eventually coined the terms for some of the most basic
principles in the field: alpha, beta, and gamma rays, the proton, the neutron,
half-life, and daughter atoms. Several of the century's giants in physics
studied under him, including Niels Bohr, James Chadwick, and Robert
Oppenheimer.
Early on he found that all known radioactive elements emit two kinds of
radiation: positively and negatively charged, or alpha and beta. He showed
that every radioactive element decreases in radioactivity over a unique and
regular time, or half-life, ultimately becoming stable. In 1901 and 1902 he
worked with Frederick Soddy to prove that atoms of one radioactive
element would spontaneously turn into another, by expelling a piece of the
atom at high velocity. Many scientists of the day scorned the idea as
alchemy. They stuck with the age-old belief that the atom is indivisible and
unchangeable. But by 1904 Rutherford's publications and achievements
gained recognition. He was an extremely energetic researcher: in the span
54
of seven years, he published 80 papers.
In 1907 he went to the University of Manchester and with Hans Geiger (of
the Geiger counter) set up a center to study radiation. In 1909 he began
experiments that were to change the face of physics. He discovered the
atomic nucleus and developed a model of the atom that was similar to the
solar system. Like planets, electrons orbited a central, sun-like nucleus.
Acceptance of this model grew after it was modified with quantum theory
by Niels Bohr. For his work with radiation and the atomic nucleus,
Rutherford received the 1908 Nobel Prize in chemistry. He was slightly put
out, since he was a physicist and felt a bit superior to chemistry! In 1914
Rutherford was knighted.
During World War I, he left his research to help the British Admiralty with
problems of submarine detection, but was soon back in the lab. He
managed to produce the disintegration of a non-radioactive atom,
dislodging a single particle. The particle had a positive charge, so it must
have come from nucleus: he called this new particle a proton. With this
experiment, he was the first human to create a "nuclear reaction," though a
weak one. In 1919 he took over as director of the Cavendish Laboratory. His
warm, outgoing personality made him an outstanding mentor to researchers
attracted there by his scientific achievements.
He took on more supervision and less direct research as years went by. In
1931 he was made the first Baron Rutherford of Nelson, allowing him to join
the House of Lords. He was fiercely anti-Nazi, and in 1933 he served as
president of the Academic Assistance Council, established to help German
refugees. He would not personally help chemist Fritz Haber, however, who
had been instrumental in creating chemical weapons in World War I.
Rutherford died two years before the discovery of atomic fission.
"All science is either physics or stamp collecting."
55
Atomic Theory
Place a checkmark next to each item that you can do! If a sample problem is given,
complete it as evidence.
_____1. I can still do
everything from Unit 1A
_____1. I can still do
everything from Unit 1B
Dalton’s Model:
_____3. I can describe
John Dalton’s
contribution to our
understanding of the
atom.
What it looked like:
Thomson’s Experiment:
_____4. I can describe
JJ Thomson’s
contribution to our
understanding of the
atom.
Thomson’s Model:
What it looked like:
Rutherford’s Experiment:
_____5. I can describe
Ernest Rutherford’s
contribution to our
understanding of the
atom.
Rutherford’s Model:
Conclusions:
Bohr’s Model:
_____6. I can describe
Niels Bohr’s
contribution to our
understanding of the
atom.
What it looked like:
56
From oldest to newest, list the models that we have used to
describe an atom.
_____7. I can state the
chronological order of
atomic models.
Particle #1
_____8. I can state the
three subatomic
particles, their location
in an atom, their
charges, and their
masses (in amu).
_____9. I can explain
why atoms are
electrically neutral.
Particle #2
Particle #3
Name
Charge
Mass
Location in
Atom
Atoms are electrically neutral because the number of
________________ is
equal to the number of _____________________.
Definitions:
mass number
_____10. I can define
mass number and
atomic number.
atomic number
In an atom of 212Po, how many protons are present?
84
_____11. Given the mass
number,
In an atom of 212Po, how many electrons are present?
I can determine the
84
number of protons,
neutron, and electrons
in an atom.
In an atom of 212Po, how many neutrons are present?
84
_____12. I can use the
Periodic Table to
determine the atomic
number of an element.
How many protons are in an atom of selenium?
How many protons are in an atom of silicon?
57
_____13. I can define
isotope.
Definition:
isotope
Write the four different methods of isotopic notation for an
_____14. I can represent atom of bromine that has 45 neutrons.
an atom in any of the
Method 2
two methods of isotopic Method 1
notation.
_____15. I can calculate
average atomic mass
given the masses of the
naturally occurring
isotopes and the percent
abundances.
Element Q has two isotopes. If 77% of the element has an
isotopic mass of 83.7 amu and 23% of the element has an
isotopic mass of 89.3 amu, what is the average atomic mass
of the element?
Definitions:
ion
cation
_____16. I can define
ion, cation, and anion.
anion
How many protons are in 19F1-?
9
_____17. Given the mass
number and the charge,
How many neutrons are in 19F1-?
I can determine the
9
number of protons,
neutrons, and electrons
How many electrons are in 19F1-?
in an ion.
9
58
Definitions:
orbital
_____18. I can ground state
define orbital,
ground state,
excited state,
excited state
electron
configuration,
and bright
line spectrum.
electron configuration
bright line spectrum
_____19. I
determine the
number of
valence
electrons for
an atom and
an ion.
_____20. I can
state the
relationship
between
distance from
the nucleus
and energy of
an electron.
_____21. I can
state the
relationship
between the
number of the
principal
energy level
and the
distance to the
atom’s
nucleus.
How many electrons does Na have?
How many electrons does Na+ have?
As the distance between the nucleus and the electron increases, the
energy of the electron __________________.
As the number of the PEL increases, the distance to the nucleus
___________
59
_____22. I can A bright line spectrum is created when
explain, in
terms of
subatomic
particles and
energy states,
how a bright
line spectrum
is created.
_____23. I can
identify the
elements
shown in a
bright line
spectrum.
Which element(s) is/are present in the mixture?
Definition:
_____24. I can valence electron
define valence
electrons.
_____25. I can
locate and
interpret an
element’s
electron
configuration
on the
Periodic
Table.
_____26. I can
identify an
electron
configuration
that shows an
atom in the
excited state.
_____27. I can
draw Lewis
electron dot
diagrams for
a given
element.
How many valence electrons does an atom of rubidium have in the
ground state?
How many energy levels does an atom of iodine have in the ground
state?
Which electron configuration represents an atom of potassium in the
excited state?
A) 2-8-7-1
B) 2-8-8-1
C) 2-8-7-2
D) 2-8-8-2
Draw the Lewis electron dot diagram for the following atoms:
Li
Be
B
C
60
N
O
F
Ne
Definition:
octet of valence electrons
_____28. I can
define and
state the
The importance of having a complete“octet of valence electrons” is
importance of
“octet of
valence
electrons.”
61
Unit 2 Practice Test 1
1) What is the total number of valence electrons in an atom with the electron configuration 2-8-5?
a) 2
b) 5
c) 8
d) 15
2) A Ca2+ ion differs from a Ca0 atom in that the Ca2+ ion has
a) more electrons
b) more protons
c) fewer protons
d) fewer electrons
3) Which particles are referred to as nucleons (subatomic particles located in the nucleus)?
a) protons and neutrons
c) neutrons, only
b) protons and electrons
d) neutrons and electrons
4) What is the mass number of an atom that contains 19 protons, 19 electrons, and 20 neutrons?
a) 39
b) 19
c) 58
d) 20
5) What term refers to the region of an atom where an electron is most likely to be found?
a) quantum
b) spectrum
c) orbital
d) orbit
6) The nucleus of an atom consists of 8 protons and 6 neutrons. The total number of electrons present in a neutral
atom of this element is
a) 6
b) 8
c) 2
d) 14
7) What is the maximum number of electrons that can occupy the third principle energy level?
a) 18
b) 8
c) 10
d) 3
8) Atoms of 16O, 17O, and 18O have the same number of
a) protons, but a different number of electrons
b) electrons, but a different number of protons
9) All atoms of an element have the same
a) number of neutrons
b) atomic mass
c) protons, but a different number of neutrons
d) neutrons, but a different number of protons
c) atomic number
d) mass number
10) The atomic number is always equal to the total number of
a) neutrons in the nucleus
c) neutrons plus protons in the atom
b) protons in the nucleus
d) protons plus electrons in the atom
11) How many protons are in the nucleus of an atom of beryllium?
a) 2
b) 4
c) 9
d) 5
12) Which subatomic particle is negative?
a) proton
b) neutron
d) nucleus
c) electron
13) Which of the following particles has the least mass?
a) neutron
b) proton
c) electron
d) hydrogen nucleus
14) A sample of element X contains 90% X-35 atoms, 8.0% X-37 atoms, and 2.0% X-38 atoms. The average
atomic mass will be closest to which value?
a) 35
b) 36
c) 37
d) 38
62
15) What is the total number of electrons in an Mg+2 ion?
a) 10
b) 24
c) 2
d) 12
16) Which of the following electron configurations represents an atom in the excited state?
a) 2-8
b) 2-8-1
c) 2-6-1
d) 2-1
17) Which principal energy level of an atom contains an electron with the lowest energy?
a) 3
b) 4
c) 1
d) 2
18) The atomic mass of an element is defined as the weighted average mass of that element’s
a) naturally occurring isotopes
c) radioactive isotopes
b) least abundant isotope
d) most abundant isotope
19) Compared to the entire atom, the nucleus of the atom is
a)
smaller and contains most of the atom’s mass
b)
smaller and contains little of the atom’s mass
20) What is the nuclear charge in an atom of boron?
a) +11
b) +6
c) +5
c) larger and contains most of the atom’s mass
d) larger and contains little of the atom’s mass
d) +12
21) What subatomic particle was discovered in the cathode ray tube experiment?
a) proton
b) electron
c) neutron
d) gravitron
Short Answer
22) In 1909, a team of British scientists led by Ernest Rutherford, carried out the Gold Foil Experiment to determine
the arrangement of particles in the atom. In this experiment, alpha particles were used to bombard gold foil.
a) Most of the alpha particles passed through the gold foil undeflected. What conclusion was made
about the structure of the atom based on this observation? (1 pt.)
b) A few of the alpha particles were deflected back at the source and toward the screen. What did
this observation reveal about the structure of the atom? (1 pt.)
23) An element has two isotopes. 90% of the isotopes have a mass number of 20 amu, while 10% have a
mass number of 22 amu. Calculate the atomic mass of the element. Show all work with units. (3 pts.)
63
24) Complete the chart below: (9 pts.)
Substance
Atom or Ion?
# protons
# neutrons
# electrons
Atomic #
Mass number
Mg+2
Rb
Cl-
25) What is the electron configuration for a neutral sulfur atom? (1 pt.)
26) What is the electron configuration for S2-? (1 pt.)
27) Based on the two given substances in question 25 and 26, how can you tell the difference between an atom
and an ion? (2 pts.)
28) Draw Bohr Diagrams for the following substances (1 pt. each):
magnesium
Na+
29) Draw Lewis Dot Diagrams for the following substances (1 pt. each):
carbon
S-2
64
30) What is the total number of valence electrons in an atom of Mg-26 in the ground state? (1 pt.)
31) What is the total number of kernel electrons in an atom of Mg-26 in the ground state? (1 pt.)
32) Write a possible electron configuration that could represent magnesium in the excited state. (1 pt.)
Bonus:
1) What are the two things you want to make sure you do when you put your goggles back in the cabinet after an
experiment? (2 pts.)
1)
2)
2) How many significant figures are there in the following number: 0.03045? (1 pt.)
65
Answer Key
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
b
d
a
a
c
b
a
c
c
b
b
c
c
a
a
c
c
a
a
c
b
22. a) Atom is mostly empty space
b.) Dense, positive core
23. 20.2 amu
24.
Substance
Atom or Ion?
Mg+2
25.
26.
27.
28.
29.
30.
31.
32.
# protons
# neutrons
# electrons
Atomic #
Mass number
Ion
12
12
10
12
24
Rb
Atom
37
48
37
37
85
Cl-
Ion
17
18
18
17
35
2-8-6
2-8-8
Same number of protons, different number of electrons
2
10
Answers will vary. 2-7-3, 2-8-1-1, 1-8-4, etc. First number in configuration can’t be greater than 2, second
number in configuration can’t be greater than 8, last number in configuration can’t be greater than 8, total
number of electrons must equal 12.
66