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Skills Worksheet
Directed Reading A
Section: The Atom
HOW SMALL IS AN ATOM?
______ 1. Which of the following statements is true?
a. A penny has about 20,000 atoms.
b. A penny has more atoms than Earth has people.
c. Aluminum is made up of large-sized atoms.
d. Aluminum atoms have a diameter of about 3 cm.
WHAT IS AN ATOM MADE OF?
Match the correct description with the correct term. Write the letter in the space
provided.
______ 2. particle of the nucleus that has no electrical
charge
______ 3. particle found in the nucleus that is
positively charged
a. electron
b. atomic mass unit
(amu)
c. nucleus
______ 4. particle with an unequal number of protons
and electrons
d. proton
e. ion
f. neutron
______ 5. negatively charged particle found outside
the nucleus
______ 6. contains most of the mass of an atom
______ 7. SI unit used to express the masses of atomic particles
HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER?
8. The simplest atom is the
atom. It has one
and one
.
9. Neutrons in the atom’s
keep two or more protons
from moving apart.
10. If you build an atom using two protons, two neutrons, and two electrons, you
have built an atom of
.
11. An atom does not have to have equal numbers of
and
.
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Introduction to Atoms
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Directed Reading A continued
12. The number of protons in the nucleus of an atom is the
of that atom.
ISOTOPES
______13. Isotopes always have
a. the same number of protons.
b. the same number of neutrons.
c. a different atomic number.
d. the same mass.
______14. Which of the following is NOT true about unstable atoms?
a. They are radioactive.
b. They have a nucleus that always remains the same.
c. They give off energy as they fall apart.
d. They give off smaller particles as they fall apart.
______15. What is the mass number of an isotope that has 5 protons, 6 neutrons,
and 5 electrons?
a. 1
c. 10
b. 11
d. 16
______16. If carbon has an atomic number of 6, how many neutrons does
carbon-12 have?
a. 12
c. 6
b. 8
d. 18
17. Most elements contain a mixture of two or more
.
18. The weighted average of the masses of all the naturally occurring isotopes of
an element is the
.
FORCES IN ATOMS
Match the correct definition with the correct term. Write the letter in the space
provided.
______19. helps protons stay together in the nucleus
a. gravitational force
______20. pulls objects toward one another
b. electromagnetic
force
______21. an important force in radioactive atoms
c. strong force
______22. holds the electrons around the nucleus
d. weak force
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Introduction to Atoms
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Section Review
The Atom
USING KEY TERMS
1. Use the following terms in the same sentence: proton, neutron, and isotope.
Complete each of the following sentences by choosing the correct term from the
word bank.
atomic mass unit
mass number
atomic number
atomic mass
2. An atom’s
is equal to the number of protons in
its nucleus.
3. An atom’s
is equal to the weighted average of the
masses of all the naturally occurring isotopes of that element.
UNDERSTANDING KEY IDEAS
______ 4. Which of the following particles has no electric charge?
a. proton
c. electron
b. neutron
d. ion
5. Name and describe the four forces that are at work within the nucleus of
an atom.
MATH SKILLS
6. The metal thallium occurs naturally as 30% thallium-203 and 70% thallium-205.
Calculate the atomic mass of thallium. Show your work below.
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Introduction to Atoms
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Section Review continued
CRITICAL THINKING
7. Analyzing Ideas Why is gravitational force in the nucleus so small?
8. Predicting Consequences Could a nucleus of more than one proton but no
neutrons exist? Explain.
INTERPRETING GRAPHICS
9. Look at the two atomic models below. Do the two atoms represent different
elements or different isotopes? Explain.
Proton
Neutron
Proton
Neutron
Electron
Electron
Copyright © by Holt, Rinehart and Winston. All rights reserved.
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Introduction to Atoms