Name: ________________
Date: 10/15/14
Period: ____
Chapter 4 Review Questions
Answer Key
Responses:
1. How did Democritus describe atoms?
Democritus described atoms as indivisible and indestructible.
2. How did John Dalton advance the atomic philosophy proposed by Democritus?
Dalton advanced the atomic theory proposed by Democritus by using experimental methods to
support his ideas.
3. What instrument is used to observe individual atoms?
The instrument used to observe individual atoms are scanning electron microscopes.
4. What are the three types of subatomic particle? Define each.
The three types of subatomic particles are protons, neutrons, and electrons.
Protons are positively charged particles located in the nucleus of an atom.
Neutrons are neutral particles (have no charge) located in the nucleus of an atom.
Electrons are negatively charged particles that are located around the outside of the nucleus in
an atom.
5. How does the Rutherford model describe the structure of the atom (discuss nucleus and empty
space-electrons)?
A positively charged nucleus surrounded by electrons, which occupy most of the volume of an
atom.
6. What are the charges and actual masses of the three main subatomic particles?
Protons have a charge of positive (+); the mass is about 1.67 x 10-24
Neutrons have no charge (0); the mass of a neutron is about 1.67 x 10-24
Electrons have a negative charge (-); the mass of an electron is about 9.11 x 10-28
7. Describe Thomson and Millikan’s contributions to the atom.
Thomson passed an electrical current through sealed glass tubes filled with gases. The resulting
glowing beam consisted of tiny negatively charged particles moving at high speed. Thomson
concluded that electrons must be parts of the atoms of all elements.
Millikan determined the charge and mass of the electron.
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Name: ________________
Date: 10/15/14
Period: ____
8. What distinguishes one atom from another atom?
Atoms of different elements contain different number of protons.
9. What does the atomic number of each atom represent?
The atomic number for each atom represents the amount of protons in that atom.
10. How do isotopes of given elements differ from each other?
Isotopes of given elements differ based on their amount of neutrons and mass numbers.
11. What equation tells you how to calculate the number of neutrons in an atom?
The equation that tells how to calculate neutrons is…. Number of neutrons = mass number –
atomic number.
12. How is atomic number different from mass number?
The atomic number is different for the mass number because it just tells you the amount of
protons, while the mass number tell you then total of the protons and neutrons.
Completion:
13. Name each picture and Label each picture with the appropriate scientist: J.J Thomson, Ernest
Rutherford, or Niels Bohr
a.
Plum Pudding Model; J.J. Thomson
b.
Nuclear Atomic Model; Ernest Rutherford
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Name: ________________
Date: 10/15/14
Period: ____
c.
Bohr Model; Niels Bohr
14. How many protons are in each of the following elements (atoms). Use a periodic table of
needed.
a. Phosphorus (P)
15
b. Molybdenum (Mo)
42
c. Aluminum (Al)
13
d. Cadmium (Cd)
48
e. Chromium (Cr)
24
f. Lead (Pb)
82
15. Determine the protons, electrons, and neutron fro elements from their chemical symbols.
a.
b.
c.
d.
e.
56
26𝐹𝑒
35
17𝐶𝑙
39
19𝐾
201
80𝐻𝑔
64
29𝐶𝑢
Protons
26
17
19
80
29
Electrons
26
17
19
80
29
3
Neutrons
30
18
20
121
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Name: ________________
Date: 10/15/14
Period: ____
16. Complete the following table.
Atomic Number
9
c. 14
e. 22
g. 25
o
o
o
Mass Number
a. 19
d. 29
47
55
Number of Protons
b. 9
14
f. 22
25
Number of Neutrons
10
15
25
h. 30
Mass Number = Number of Protons (atomic number) + Number of Neutrons
Number of Neutrons = Mass Number – Number of Protons (atomic number)
Atomic Number (Number of Protons) = Mass Number – Number of Neutrons
17. Lithium has two isotopes: Lithium-6 (atomic mass= 6.015, relative abundance = 7.5 %) and
Lithium-7 (atomic mass = 7.016, relative abundance = 92.6 %).
Calculate the atomic mass of lithium.
Atomic Mass of Lithium = (6.015 x 0.075) + (7.016 x 0.926)
= 0.45 + 6.50
= 6.95
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