KEY # ___
Unit 6 STAR Review Answers
Section 6A Supplement
Fill in the blanks in the table below:
Isotopic
notation
Element name
Atomic
Number
Mass
number
Number of
protons
Number of
neutrons
Cobalt
27
59
27
32
3.
59
4.
127
I
Iodine-127
53
127
53
74
5.
46
Ti
titanium-46
22
46
22
24
6.
242
plutonium-242
94
242
94
148
Co
Pu
9. Are the following statements true or false?
a. ___F____ An element with an atomic number of 29 has 29 protons, 29 neutrons, and 29
electrons.
b. ___T____ An atom that is an isotope of 60Fe has 34 neutrons. (26 protons is iron!!)
c. ____F_____ An atom of 31P contains 15 protons, 16 neutrons,(true) and 31 electrons.
d. _____T____ 23Na and 24Na are isotopes. (same element diff neutrons (diff mass #)
e. ___F______ 24Na has one more electron than 23Na
f. _____T____ 24Na has one more neutron than 23Na. (mass # +1)
10. Rank protons, neutrons and electrons according to their mass. Protons and neutrons about the
same. Electrons are almost nothing. (1/1840) a.m.u.
Section 6A Supplement
Is it possible for two atoms of C to have different mass numbers? Explain. Yes, same protons, diff #
neutrons. (isotopes)
Is it possible for two atoms of C to have different atomic numbers? Explain.
No, change atomic # it’s a new element!! Carbon ALWAYS has 6 protons!!
11. Complete the following table:
Isotopic
# of Protons
notation
# of Neutrons
Mass Number
Element Name
1
1
2
Hydrogen-2
Cl
17
20
37
Chlorine - 37
Tc
43
56
99
Technitium - 99
a.
2
1
b.
37
17
c.
99
43
d.
137
55
Cs
55
82
137
Cesium – 137
e.
107
47
Ag
47
60
107
Silver-107
H
KEY # ___
12. Hydrogen-3 is radioactive; however, hydrogen-1 is not. Identify differences in these two atoms that
are responsible for differences in their nuclear properties.
_________________________________________________________________________________
Hydrogen-3 has 1 proton and 2 neutrons (unstable); Hydrogen-1 has 1 proton and 0 neutrons
(stable).
13. What is the atomic weight of silicon, if 92.2% of its atoms have mass 28.0 g/mol, 4.7% have mass
29.0 g/mol, and 3.1% have mass 30.0 g/mol?
(92.2%)(28.0) + (4.7%)(29.0) + (3.1%)(30.0) = 28.1 g/mol.
Element’s Atomic Weight = Sum of ∑ (%)(atomic mass) of each isotope
6B.5 and 6B.6 Supplement: Nuclear Balancing Act
Write a balanced equation for each of the following nuclear reactions.
Examples:
Chlorine-36 decays by beta emission
Dubnium-262 decays by alpha emission
36
36
0
4
262
258
17Cl  18Ar + -1e
105 Db 103 Lr + 2 He
87
36
1. Krypton-87 decays by beta emission.
240
96
2. Curium-240 decays by alpha emission.
3. Uranium-232 decays by alpha emission.
4. Silicon-32 decays by beta emission.
32
14
36Kr 
Cm 
232
92
U
Si 
32
15
236
94
87
37
Rb 
Pu 
4
2
0
-1
e
He
Th  42 He
228
90
P
0
-1
e
6C.6 Supplement: Nuclear Bombardment Reactions
Write a balanced equation for each of the following nuclear reactions.
Example: Oxygen-16 plus a neutron results in the formation of another element and the release of an
alpha particle.
16
1
13
4
8 O + 0 n  6 C + 2 He
8. Plutonium-239 can be produced by bombarding
uranium-238 with an alpha particle. Some neutrons
are released.
238
92
9. Uranium-235 is bombarded with a neutron to
produce tellurium-137, another element, and 235
92 U 
two neutrons.
1
0
U  42 He 
n
Te 
137
52
10. On the sun, three steps are needed to create helium
from hydrogen (nuclear fusion). In the third step, two 23 He  23 He 
helium-3 atoms react to form helium-4 and two hydrogen atoms.
239
94
Pu  3 01 n
97
40
Zr  2 01 n
4
2
He  2 11 H
___________________________________________________________________________
KEY # ___
Section 6D Supplement
1. 1.8 x 1017 kg m2/s2 = 1.8 x 1017 J or 1.8 x 1014 kJ
2. A major daily resource Americans use, electricity, is generated from nuclear energy. Atomic weapons
are also created from nuclear energy.
1. Which two quantities are conserved during nuclear reactions?
Mass and energy are conserved, although a very small amount of mass is converted to energy. Thus,
Einstein created the equation, E=mc2 where energy released (E) equals the mass lost (m) multiplied
by the speed of light squared (c2).
2. What is the source of the energy produced during nuclear fission?
A very heavy atom, usually uranium-235, is struck with a neutron which then splits the chosen atom’s
nucleus, releasing a vast amount of energy and creating smaller atoms and a few neutrons. The
energy is derived from the strong force, which holds the protons and neutrons together in the nucleus.
The strong forces in the nuclei of the products are greater than the strong force in the nucleus of the
atom that was split.
3. Protons and neutrons both reside in the nucleus. What holds these particles together?
The strong force holds these particles together in the nucleus, extending only across an atom’s
nucleus.
4. How much energy would be released if 2.0 kg of matter were fully converted into energy?
E = 2.0 kg (3.0 x 108 m/s)2
E = 1.8 x 1017 kg m2/s2 = 1.8 x 1017 J or 1.8 x 1014 kJ
5. What have been the two major uses for the energy produced in nuclear fission?
A major daily resource Americans use, electricity, is generated from nuclear energy. Atomic weapons
are also created from nuclear energy.