Download Honors Chemistry

Arnoldi
Chemistry
Atomic Theory One
Note Sheet Answer Key
I. Atomic Theory Background Information
A. What is an atom?
1. Atoms are the _________________________ of matter.
2. An atom is the _________________________ that still
retains the properties of that element.
B. Important Definitions
1. _______________ (Z): # of protons in the nucleus
a. The atomic number is the _____ number on the periodic table.
(the PT is arranged by atomic number)
b. The atomic number controls the _________________.
(the identity of the atom is based on the
number of protons in the atom)
2. ___________:
a.
the sum of the protons and neutrons in the nucleus
This is the mass for _________________.
b. Mass Number is ______ on the Periodic Table.
3. Subatomic Particles:
a. Atoms are made up of ________________________.
b. Table
Particle
Charge
Mass (Two Ways)
Location in Atom
Proton
+
1 amu
# In Nucleus
Electron
-
Negligible
*Outside of Nucleus
Neutron
neutral
1 amu
# In Nucleus
# Nucleons:
(____________ and
_____________)
* Electrons are actually found in _______________.
What is the nucleus? The nucleus is the small, dense, positively
charged __________________.
4. ________
a.
atoms with a charge / charged particles
_____________ control the charge of the particle.
When the number of protons and electrons in the atom is
the same, the atom is _____________.
When the number of protons and electrons in the atom is
______________, an ion exists.
Since protons cannot be changed without changing the
identity of the atom, it is electrons that are ________
or ____________ when forming ions.
b. ___________:
negatively charged particles
Anions are formed when electrons are ________.
c.
___________: positively charged particles
Cations are formed when electrons are ________.
5. _________: atoms of the same element with different masses
Remember, only protons and neutrons have significant
mass. Since protons cannot be changed without changing
the identity of the atom, isotopes occur when atoms of
the same element have different numbers of neutrons.
a. An Example: The Three Hydrogen Isotopes
Hydrogen
Protium
Deuterium
Tritium (artificial
Isotopes
and radioactive)
Protons
1
1
1
Neutrons
0
1
2
Electrons
1
1
1
Mass
1 amu
2 amu
3 amu
% Abundance
99.85%
.15%
0%
b. How do we write an isotope?
12
Carbon – 12
C
6
12
or
C
Carbon / C is the identity of the element.
___ is the mass number.
___ is the atomic number.
d. How do we determine protons, electrons and neutrons?
look on the _________
Protons = Atomic Number
Electrons = protons if the atom is _______________.
If the atom is charged…
Positive ions have _____ electrons than protons.
Negative ions have _____ electrons than protons.
Neutrons =
Isotope
Protons
Electrons
Neutrons
40 +1
K
12
14
C
S-2
12
38
36
53
9
10
10
PROMPT ONE
Use this table to answer the following questions:
Particle
Protons
X
17
Y
17
Electrons
17
17
Neutrons
18
19
(a) Explain why these two particles are the same element. (sentences, s/g)
(b) Explain why these two particles are called isotopes. (sentences, s/g)
(c) What is the mass number of particle X? Explain how you determined this answer. (sentences, s/g)
PROMPT TWO
Use this table to answer the following questions:
Particle
Protons
X
17
Y
17
Electrons
17
18
(a) Write the isotope/ion designation for each of the particles.
(b) Explain why the Y particle is called an ion. (sentences, s/g)
Neutrons
18
19
6. __________:
a.
the average mass of the isotopes of an element
aka
Classroom Height Example
b. Equation
Average atomic mass =
EXAMPLES:
[(% abundance)(mass of 1st isotope)]
+ [(% abundance)(mass of 2nd isotope)]......
100
What is the atomic mass for element B?
11
B = 80.20%
10
B = 19.80%
PROMPT THREE
Given the following information, what is the average atomic mass of neon (to five decimal places)?
Isotope
Exact Mass (amu)
Percent Abundance
Neon – 20
Neon – 21
Neon – 22
19.99244
20.99395
21.99138
90.51
.27
9.22
II. Early Atomic Theories
A. Democritus:
1. 460 BC, Greek
2. First person to use the term “______”, which means ________.
3. He also thought atoms were ______ and ______________.
4. There is _______________________ to support his ideas.
B. John Dalton
1. English, 1803
2. Dalton’s Main Ideas About Atomic Theory
a. All matter is made up of _______ which are _________
and ___________.
b. Atoms of the same element are _________________ – in
particular their _________ are the same. Atoms of different
elements are _____________ different, in particular their
_____________ are different.
c. Atoms combine in _________________________
(by mass) to form compounds.
3. Billiard Ball Model
4. What part of Dalton’s theory do we still believe?
a. Matter ________ made of atoms.
b. Atoms ______________ in simple whole number ratios.
c. Chemical rxns _________________ of the separating /
combining of atoms.
5. What part of Dalton’s theory do we not believe?
a. Atoms are ___________. They can be divided into subatomic
particles, (protons, electrons and neutrons).
b. Atoms are ___________ in nuclear reactions (we can create
atoms in nuclear reactions, also).
b. Atoms of different elements ___________________, and
______________________ can have different masses. This
occurs because of isotopes.
12
C vs. 13C
14
C vs.
14
N
PROMPT FOUR
Write three important contributions towards atomic theory for each of the following:
(a) Democritus
(b) John Dalton
III. Developing Atomic Theories
A. J J Thomson
1.
1890s, English
2. Used Crookes’ (another scientist) Tube to discover the electron.
3. Diagram:
X
4. Explanation
J J Thomson took a cathode ray tube and applied a magnetic field.
When a negative field was introduced, the cathode ray was
___________________. When a positive field was
introduced, the cathode ray was _______________. From
this, Thomson concluded that the cathode ray was composed of a
stream of _______________________, which he called
________________.
5. Model – Plum Pudding
C. Rutherford
1. 1911, New Zealand
2. Rutherford used the ____________________ to discover
evidence for a nucleus.
3. Diagram
Alpha Particles
a few were deflected
Gold Foil
most
go
through
5. Description
Rutherford bombarded gold foil with ________________.
Most of the particles __________________. A few were
___________. Since alpha particles are ____________
and they were deflected, not attracted, they must have hit
something positive inside of the atom (likes repel). Rutherford
concluded that there is a _______________________
center in the atom, which he called the ____________. The
rest of the atom is ______________________.
Analogy: if an atom is the size of the Eagle’s stadium, then the
nucleus is the size of a tennis ball floating in the middle of the
stadium.
6. So, where are the electrons?
The electrons are somewhere ____________________
occupying most of the volume of the atom.
*If electrons are negative, and the center
of the atom is positive, why aren’t they
attracted to the center of the atom?
7. Model
PROMPT FIVE
Write three important contributions towards atomic theory for each of the following:
(a) Thomson
(b) Rutherford
D.
Niels Bohr
1. Bohr began to explain the location of electrons as accepted today.
This is a _____________________ of what is really happening.
2. Electrons reside in __________________, aka energy shells.
3. The energy of the electron shell and the distance of the shell from the
nucleus are __________________. (The energy of the level
___________________ as the distance from the nucleus increases).
4. Electrons fill the energy levels from the ____________, which
means the first energy shell is filled before electrons enter the second
shell, the second energy level is filled before electrons enter the third
shell, etc. This means that electrons fill shells ________________.
4. Bohr Diagrams give us a quick look at how the electrons are arranged.
a. Basic Pattern
# of
Protons
shows the _________ number of electrons
allowed in the energy levels
)2e-
)8e-
b. Examples
(i). Sodium Atom
(ii). Sodium Ion (+1)
(iii). Chlorine Atom
(iv). Chlorine Ion (-1)
)8e-
5. Ground vs. Excited States
a. An atom occupies the _______ state if it is in the _______
possible energy state. This occurs if the first shell is filled
before electrons are placed in the second shell, the second shell
is filled before electrons are placed in the third shell, etc.
b. An atom is considered to be in the _________ state if it
is ______ in the lowest possible energy state. This
occurs if one of the inner shells is not completely filled
before moving to the next shell.
c. The ground state is also called the _________ state.
The excited state is also called the _________ state.
6. To move from one energy level to another, you must _________
__________ amount of energy between those two levels.
PROMPT SIX
Explain why each of the following Bohr diagrams is correct or incorrect.
Potassium Atom
Oxygen Ion (-2)
19p
) 2e- )8e- )8e- )1e-
8p
)2e- )4e-
11 p
)8e- )2e-
Sodium Ion (+1)
E. Comparing Modern Atomic Theory to Dalton’s Atomic Theory
1. Similarities
matter _____ composed of atoms
atoms ___ combine in simple whole number ratios
2. Differences
atoms are divisible (_________________)
atoms are destructible (______________)
atoms of the same element sometimes have
different masses and atoms of different
elements sometimes have the same mass
(___________)
Electrons are in a region of high probability called
an _____. They are not in an exact shell location.
IV. What experimentation led us to understand the location of electrons?
A. Spectroscopy
B. Some Important Definitions
1.
All of the frequencies and wavelengths of electromagnetic radiation.
2.
The uninterrupted broad band of all colors (one color blends into the next).
3.
The spectrum where distinct lines of color appear.
Each color corresponds to distinct _________________.
The can be used like a _______________ for the element.