Download Understanding the Atom

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Date
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Understanding the Atom
3.1 Discovering Parts of an Atom
Directions: On the line before each statement, write correct if the statement is correct
or not correct if the statement is not correct. If the statement is not correct, change
the underlined word(s) to make it correct.
(30 points this side)
_______
1. Early Greek philosophers, such as Democritus,
thought that all matter was made of fire, water, air, and
earth.
_______
2. John Dalton’s atomic theory supported some of the
ideas of Aristotle.
_______
3. An atom is the smallest piece of an element that still
represents the element.
_______
4. Atoms are so small that about 7.5 million carbon
atoms could fit into the period at the end of this
sentence.
_______
_______
5. An electron is a particle with one negative charge.
_______
7. Niels Bohr discovered the existence of neutrons, or
neutral particles, in the nucleus of an atom.
_______
8. According to the modern atomic model, electrons
form an electron cloud around the nucleus.
_______
9. Modern scientists believe that protons and neutrons
are not made of smaller particles.
6. Rutherford’s atomic theory stated that most of an
atom’s mass is concentrated in the nucleus.
Matching
Directions: On the line before each definition, write the letter of the term that
matches it correctly. Not all terms are used.
Write the terms NOT USED and a definition.
A. nucleus
1. particle with one negative charge
2. smallest particle of an element
that still represents that element
3. particle with one positive charge
4. neutral particle found in the
nucleus
B.
C.
D.
E.
F.
electron
neutron
proton
quark
atom
Directions: Label this diagram by writing the correct term from the word bank on each line.
electron cloud
neutron
nucleus
proton
Directions: Answer each question.
10. Is it possible to see atoms with your eyes? Explain.
11. What is an STM?
12. How have STMs helped scientists study atoms?
1
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Name____________________
A. Early Ideas About Matter (40 points this side)
1. Many ancient Greek philosophers thought that all matter was made
of only four elements—fire, water, air, and _______.
2. These early scientists were not able to ______ their theories.
3. Democritus proposed that matter is made of small, indivisible objects
4. He proposed that different types of ________________ are
made from different types of atoms.
B. Dalton’s Atomic Model
1. John Dalton proposed the _________ theory, which was based
on careful observations and __________ of chemical reactions.
2. Dalton’s theory states that atoms cannot be divided,
foil, but some bounced to the ____________, and a few bounced
straight back.
3. Rutherford’s resulting atomic model proposed that most of an atom’s
____________ and ____________ charge is concentrated in
___________, or destroyed.
It also stated that atoms of one ____________ are different
from atoms of other ____________.
a. The ________________ is the small, positively charged
area in the center of the atom.
b. In the nucleus is the ____________, which is an atomic
particle with one positive charge.
F. Discovering Neutrons
1.
2.
1. The atomic model of _______proposed that __________
move in circular orbits, or __________, around the nucleus.
2. When energy is added to an atom, electrons move to higher
1. A(n) _________ is the smallest piece of an element that still
represents that element.
2. Atoms were first seen by using a(n) _________________
microscope.
D. Thomson—Discovering Electrons
1. Thomson discovered that the rays in a(n) ____________ were
____________; when energy is released by the electron, it
moves back to a lower level.
3. The limitation of Bohr’s model is that electrons do not actually move
in
orbits.
H. The Modern Atomic Model
attracted to a(n) ____________ charged plate, which means
1. In modern atomic theory, electrons form a(n) ___________,
that the rays have a(n) ____________ charge.
2. Thomson’s atomic model stated that an atom is a positively charged
which is an area around the ____________ in which an
electron is likely to be located.
____________ with ____________ throughout it.
E. Rutherford—Discovering the Nucleus
1. Rutherford’s student performed an experiment during which they
shot ___________ particles into a piece of ___________
foil.
Utah Core Curriculum Standard I
____________ was one of Rutherford’s colleagues.
Chadwick discovered the ____________, a neutral particle
that exists in the ____________ of an atom.
G. Bohr’s Atomic Model
C. The Atom
2
Date
Period
The results showed that most of the particles traveled through the
the center of the atom.
called ____________.
3.
2.
I.
2. An electron cloud is mostly ____________ space.
Quarks
1. Protons and ____________ are made of smaller parts called
____________.
2. There are ____________types of quarks.
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(30 points this side)
Name____________________
Date
Period
Directions: Complete the crossword puzzle with the correct terms from the word bank.
Atomic Theory Magic Square
Put the number of the definition from the list below on the line in the
square with the appropriate term. Check your answers by adding the
numbers in each row and column.
They should add up to the same number.
Democritus _____
Dalton _____
Thomson _____
element _____
Rutherford _____
proton _____
atom _____
Bohr _____
quark _____
neutron _____
nucleus _____
alpha particle _____
electron _____
Chadwick _____
energy levels _____
electron cloud _____
1. current explanation of where electrons might be found in the atom
2. English schoolteacher who proposed the atomic theory model of
matter
3. proposed the plum-pudding model of the atom; discovered the
electron
4. the negative particle that circles the nucleus
5. developed the model of the atom in which electrons orbit the
nucleus in energy levels
6. the neutral particle in the nucleus of an atom
7. the tiny positive core of an atom; contains protons and neutrons
8. discovered the nucleus using his gold foil experiment
9. small particles that make up protons and neutrons
10. the smallest particle of an element that has the properties of that
element
11. the positive particle in the nucleus of an atom
12. used by Rutherford in his experiment; made of two protons and two
neutrons
13. Greek philosopher who made a mental model of the atom
14. the paths in which electrons circle the nucleus according to the Bohr
model
15. discovered the neutron
16. building blocks of matter represented by a symbol
atoms electron
electron cloud
neutron
nucleus proton
Down
2. area around the nucleus where an
electron is most likely to be
4. neutral particle that exists in the
nucleus of an atom
Across
6. smallest pieces of elements that still
represent those elements
1. particle with one negative charge (1–)
3. small area in the center of an atom
that contains most of the atom’s mass
5. particle with one positive charge (1+)
3
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(45 points this side)
Name____________________
3.2 Protons, Neutrons, and Electrons—How Atoms Differ
A. The Parts of the Atom
1.
___________ and ___________ have about the
same mass
2.
___________have much less mass than the other two particles
in an atom.
3. Most of the mass of an atom is in the ___________.
B. Different Elements—Different Numbers of Protons
1. The number of protons in an atom of an element is the element’s
___________.
2. Different elements contain different numbers of ___________.
3. In a neutral atom, the number of ___________ equals the
number of protons because the number of __________charges
must equal the number of positive charges.
C. Neutrons and Isotopes
___________ are atoms of the same element that have
different numbers of ___________.
2. The total number of ___________ and neutrons in an atom is
the ___________of the atom.
3. The ___________ of an element is the average mass of the
element’s ___________.
a. The average atomic mass is ___________ according to the
___________of each atom in a sample and the number of
atoms of that ___________that are present.
D. Radioactivity
1.
______________first noticed that some elements
spontaneously give off energy.
2.
______________________ called elements that
Period
3. Radiation is made of energy and ___________ that come from
the ___________ of radioactive atoms.
4. When atoms release particles of radiation, they change to
different ___________.
5.
_______________ ___________is a process that
occurs when an unstable ___________ changes into another,
more stable nucleus by emitting radiation.
a. Nuclear decay can produce three different types of
___________.
b. A(n) ___________ particle consists of___________
protons and two ___________.
c. When alpha decay occurs, the atomic number of each atom that
decays ___________ by ___________.
d.
1.
abundance of each isotope.
b. Weighted means that the average atomic mass is based on the
Date
___________ decay occurs when a neutron in an atom
changes into a(n) ___________ and a high-energy electron
called a(n) ___________ particle.
e. When beta decay occurs, the atomic number of an
atom___________ by ___________.
f. Gamma rays contain a lot of ___________ but no particles..
g.
___________rays are sometimes emitted during nuclear
decay, but this decay does not change one element into another
element.
6. Energy released during radioactive decay can be
either___________ or harmful.
E. Ions—Gaining or Losing Electrons
1. A(n) ___________is an atom that is no longer neutral because
it has gained or lost ___________.
2. A positive ion is an atom that has ___________ electrons.
3. A negative ion is an atom that has ___________ electrons.
spontaneously emit radiation radioactive.
4
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Name____________________
Atomic Structure (42 points this column)
Use Percentages
_______________.
The mass number of an atom is the sum of the number of ______________ and the
100 and then divide. For example, 25% equals
The atomic number represents the number of _______________.
2.
In a neutral atom the number of protons is always equal to the number of
number of ______________.
Use a copy of the periodic table in your planner and the information given in the data table
to fill in the blanks. (1 point each blank square) Extra credit: draw and label any of the atoms.
Substance
Symbol
Atomic
Number
Mass
Number
Number
of
Protons
2 4
Mg 12
Zinc
30 65
Bromine
80
Al
13
Uranium
Sodium
11
Kr
Calcium
40 20
Ag
47
Gold
79 197
Copper
64
Number
of
Neutrons
Number
of
Electrons
Helium
5
Period
Percentages compare a partial amount to a whole amount, much like a
fraction. The whole amount is equal to 100%. To change a percentage into
a decimal, first write the percentage as a fraction with a denominator of
1.
3.
Date
50 points this page
Utah Core Curriculum Standard I
A weighted average is a calculation based on the abundance, in
percentages, of the items being averaged. Follow the steps below to
calculate the weighted average atomic mass of an element.
Copper (Cu) exists naturally in two isotopes. If copper is made up of
69.17% Cu-63 and 30.83% Cu-65, what is the average atomic mass of Cu?
Step 1 Change each percentage to a decimal.
69.17%
12
25
, which is equal to 0.25.
100
= 0.617
100
30.83%
= 0.3083
100
35
14
146 92
12
48 36
61
Step 2 Multiply the mass of each isotope by its decimal percentage.
63 × 0.6917 = 43.5771
65 × 0.3083 = 20.0395
Step 3 Add the values together to get the average atomic mass.
43.5771 + 20.0395 = 63.62
Practice (8 points this column)
1. Boron (B) contains 19.9% B-10 and
80.1% B-11. What is the average
atomic mass of boron?
2. If 50.69% of bromine (Br) is Br-79 and
49.31% is Br-81, what is the average
atomic mass of bromine?
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3. Silicon (Si) contains 92.23% Si-28,
4.67% Si-29, and 3.10% Si-30. What
is the average atomic mass of Si?
4. If selenium (Se) is 0.89% Se-74,
9.36% Se-76, 7.63% Se-77, 23.78% Se78, 49.61% Se-80, and 8.73% is Se-82,
what is the average atomic mass of
Se?
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Name____________________
Protons, Neutrons, and Electrons−How Atoms Differ
Directions: Use your textbook to answer each question. (5 points each sentence)
1. Atoms are composed of particles called protons, neutrons, and
electrons.
Describe the relative mass, the charge, and the location within the
atom of protons, neutrons, and electrons.
2. There are 115 different elements. Each has its own distinct
properties.
Describe the way atoms of elements differ.
3. Most elements have different isotopes.

Date
Period
Key Concept How does a neutral atom change when its number
of protons, electrons, or neutrons changes?
Directions: Label this diagram by writing the correct number of electrons and protons
on each line. Then use the diagram to answer each question on the lines provided.
1.
3.
2.
4.
5.
7.
Identify how atoms of isotopes differ from one another.
8.
6.
4. Some elements have an unstable nucleus that changes into a more
stable nucleus through nuclear decay.
Identify and describe three types of nuclear decay.
9. What does the diagram show?
5. Neutral atoms sometimes gain or lose electrons. Atoms that are no
longer neutral because they have gained or lost electrons are
called ions.
Describe the charge on an atom that has lost electrons. Then
describe the charge on an atom that has gained electrons.
10. What happened to the electrical charge of each atom in the diagram?
11. The top left diagram shows sodium (Na). The bottom left diagram
shows fluorine (F). Which symbols would you use to represent the
top right diagram and the bottom right diagram?
6
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Radioisotopes
Date
20 points this page
You have learned that some isotopes of elements are radioactive. These are called
radioisotopes. Radioisotopes are unstable, so they undergo decay by giving off radiation
as matter and/or energy until they reach a more stable state.
Half-Lives
The rate at which radioisotopes of various elements decay is described as the half-life
of the isotope. One half-life is the time it takes for one-half the atoms in a sample to
decay. Half-lives for various radioisotopes can range from less than a second to billions of
years. The table shows the half-lives for a number of radioisotopes. The number after
each name is the isotope’s atomic mass.
Radioisotope
Half-life
Polonium-215
0.0018 seconds
Barium-139
86 minutes
Iodine-131
8.07 days
Cobalt-60
5.26 years
Carbon-14
5,730 years
Uranium-238
4.5 billion years
Applying Critical-Thinking Skills
1. Solve You began with 100 g of cobalt-60. How
much cobalt-60 remains after 21.04 years?
2. Explain The uranium used in fuel rods in nuclear
power plants eventually decays to the point
where it doesn’t give off enough energy to be
practical. Why might disposing of these rods be a
problem if they contain uranium-238?
3. Make a bar graph showing how much is left after
Using Half-Lives
Suppose you begin with 10 g of barium-139, which decays to become
lanthanum-139. After one half-life (86 minutes), you would have 5 g of barium-139 and 5
g of lanthanum-139. After another 86 minutes, half of the remaining 5 g of barium-139
would decay into lanthanum-139. You would now have 2.5 g of barium-139 and 7.5 g of
lanthanum-139. How can we use this idea?
Carbon Dating
The half-lives of radioisotopes can help scientists determine the age of very old
artifacts. For example, scientists can use the half-life of carbon-14 (C-14) to determine the
approximate age of organic objects that are less than 40,000 years old. All living organisms
contain a fixed percentage of the radioisotope C-14. When an organism dies, the C-14 is
not replaced, but it continues to decay. By determining how much of the carbon-14
remains, scientists can calculate the age of a sample. This is known as carbon dating.
Isotopes with longer half-lives such as uranium-238 can be used to date older objects
such as igneous rocks.
7
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six half-lives.
105%
90%
75%
60%
45%
30%
15%
Begin 1
2
3
4
5
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Date
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Understanding the Atom
Directions: On the line before each statement, write correct if the statement is correct or not
correct if the statement is not correct. If the statement is not correct, change the underlined word(s)
to make it correct.
_______
_______
_______
1. Carbon-12, carbon-13, and carbon-14 are
examples of atoms of the same element that have
different numbers of neutrons. _______
1. A proton has a charge of 1-.
2. Neutrons and protons have the same relative mass.
3. The number of electrons in an atom of an element is the element’s
2. Radioactive elements emit radiation without
external force or cause.
_______
atomic number.
_______
_______
4. Neutral atoms have the same number of protons and electrons.
3. Nitrogen’s number of protons is seven.
_______
5. Carbon-12 and carbon-13 are isotopes, so they have different
numbers of neutrons.
_______
Period
Directions: On each line, write the term that correctly
replaces the underlined words in each sentence.
6. The mass number of an atom can be determined by adding the
number of electrons and the number of neutrons.
4. A radioactive element goes through a process in
which its unstable atomic nucleus changes into
another more stable nucleus by emitting
radiation. _______
Key Concept How has the atomic model changed over time?
Directions: Place the events in chronological order from earliest to most recent by writing a
number 1 through 7 on the line before the statement that describes each event.
_____
_____
J.J. Thomson investigates the electrical charges of atoms.
5. Beneath each element’s symbol on the periodic
table, there is a number that provides the average
mass of the element’s isotopes, weighted
according to the abundance of each isotope for
the element. _______
Democritus challenges the popular idea that matter is made of fire, water, air,
and earth.
_____
_____
_____
Niels Bohr investigates the energy level of electrons.
John Dalton finds evidence to support the theory that all matter is made of
7. Uranium is an example of an element that is able
to spontaneously emit radiation. _______
Scientists discover that protons and neutrons are made of quarks.
James Chadwick discovers that in addition to protons, the nucleus also
contains neutrons.
8
electrons. _______
Students of Ernest Rutherford conduct the gold foil experiment.
atoms that cannot be divided, created, or destroyed.
_____
_____
6. Na+ and F– are examples of atoms that are no
longer neutral because they have gained or lost
Utah Core Curriculum Standard I
8. Carbon-12 is the most abundant isotope of the
element; it has a sum of protons and neutrons
equal to 12. _______
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