Atoms and Elements
2
Answers and Solutions to Text Problems
2.1
a. Cu
e. Fe
b. Si
f. Ba
c. K
g. Pb
d. N
h. Sr
2.2
a. O
e. H
b. Li
f. Ne
c. S
g. Sn
d. Al
h. Au
2.3
a. carbon
e. fluorine
b. chlorine
f. argon
c. iodine
g. zinc
d. mercury
h. nickel
2.4
a. helium
e. calcium
b. phosphorus
f. bromine
c. sodium
g. cadmium
d. magnesium
h. silicon
2.5
a. sodium and chlorine
b. calcium, sulfur, and oxygen
c. carbon, hydrogen, chlorine, nitrogen, and oxygen
d. calcium, carbon, and oxygen
2.6
a. hydrogen and oxygen
b. sodium, hydrogen, carbon, and oxygen
c. sodium, oxygen, and hydrogen
d. carbon, hydrogen, and oxygen
2.7
a. Period 2
b. Group 8A (18)
c. Group 1A (1)
d. Period 2
2.8
a. Group 1A (1)
b. Period 2
c. Group 8A (18)
d. Group 7A (17)
2.9
a. alkaline earth
d. alkali metal
b. transition element
e. halogen
c. noble gas
2.10
a. noble gas
d. halogen
b. alkaline earth metal
e. alkaline earth metal
2.11
a. C
b. He
c. Na
d. Ca
e. Al
2.12
a. Be
b. P
c. Kr
d. I
e. Ge
2.13
On the periodic table, metals are elements located to the left of the heavy zigzag line, while the
nonmetals are elements to the right.
a. metal
b. nonmetal
c. metal
d. nonmetal
e. nonmetal
f. nonmetal
g. metal
h. metal
2.14
a. metal
e. nonmetal
b. metal
f. nonmetal
c. nonmetal
g. nonmetal
d. metal
h. metal
2.15
a. electron
b. proton
c. electron
d. neutron
2.16
a. neutron
b. proton and neutron
2.17
The two most massive subatomic particles, protons and neutrons, are located in a very small
region of the atom, which is called the nucleus.
c. transition element
c. electron
d. electron
Chapter 2 Answers and Solutions
2.18
Because protons are present in the nucleus of every element and protons are the positively
charged subatomic particles.
2.19
Selection b (a proton and an electron) is the only one with a pair of particles having opposite
charges.
2.20
Selections a (two protons) and c (two electrons) are pairs of particles having the same charge.
2.21
Because the hair strands repel one another, there must be like electrical charges on each strand.
2.22
Because the clothes cling to each other, there must be opposite electrical charges on the clothing.
2.23
a. atomic number
2.24
a. number of protons and electrons, if a neutral atom
b. number of particles (protons plus neutrons) in the nucleus
c. number of neutrons
d. nothing useful
2.25
a. lithium, Li
e. neon, Ne
b. fluorine, F
f. silicon, Si
c. calcium, Ca
g. iodine, I
d. zinc, Zn
h. Oxygen, O
2.26
a. hydrogen, H
e. bromine, Br
b. sodium, Na
f. silver, Ag
c. potassium, K
g. phosphorus, P
d. iron, Fe
h. helium, He
2.27
a. 12
b. 30
c. 53
d. 19
2.28
a. 6
b. 9
c. 20
d. 16
2.29
Name of
Element
Aluminum
Magnesium
Potassium
Sulfur
Iron
2.30
Name
of
Element
Nitrogen
Calcium
Strontium
Silicon
Barium
2.31
Symbol
Al
Mg
K
S
Fe
b. both
Atomic
Number
13
12
19
16
26
c. mass number
Mass
Number
27
24
39
31
56
Symbol
Atomic
Number
Mass
Number
N
Ca
Sr
Si
Ba
7
20
38
14
56
15
42
88
30
138
Number of
Protons
13
12
19
16
26
Number
of
Protons
7
20
38
14
56
d. atomic number
Number of
Neutrons
14
12
20
15
30
Number
of
Neutrons
8
22
50
16
82
Number of
Electrons
13
12
19
16
26
Number
of
Electrons
7
20
38
14
56
a. Since the atomic number of aluminum is 13, every Al atom has 13 protons. An atom of
aluminum with a mass number 27 and an atomic number 13 has 14 neutrons.
27 − 13 = 14 n Therefore, 13 protons, 14 neutrons, 13 electrons
b. 24 protons, 28 neutrons, 24 electrons
c. 16 protons, 18 neutrons, 16 electrons
d. 26 protons, 30 neutrons, 26 electrons
Atoms and Elements
2.32
a. 1 proton, 1 neutron, 1 electron
b. 7 protons, 7 neutrons, 7 electrons
c. 14 protons, 12 neutrons, 14 electrons
d. 30 protons, 40 neutrons, 30 electrons
2.33
a. 31P
b. 80Br
15
2.34
a. 18 O
a. 32S
16
d. 35Cl
13
17
b. 9 Be
c. 56 Fe
d. 24 Na
4
26
11
8
2.35
c. 27Al
35
33
S
34
36
16
16
S
16
S
b. They all have the same atomic number, (the same number of protons and electrons).
c. They have different numbers of neutrons, which is reflected in their mass numbers.
d. The atomic mass of sulfur on the periodic table is the average atomic mass of all the naturally
occurring isotopic masses.
2.37
To calculate the average atomic mass of an element, I would need the actual mass and the
percent abundance of each naturally occurring isotope.
2.38
a.
84
86
38
38
Sr
Sr
87
88
38
38
Sr
Sr
b. They all have the same atomic number, (the same number of protons and electrons).
c. They have different numbers of neutrons, which is reflected in their mass numbers.
d. The atomic mass of strontium on the periodic table is the weighted average of all the
naturally occurring isotopic masses.
2.39 69 (60.1/100) = 41.5
2.40
71 (39.9/100) = 28.3 thus 41.5 + 28.3 = 69.8 amu (average mass)
84 (0.0056) = 0.47 86 (0.0986) = 8.48 87 (0.0700) = 6.09
total = 0.47 + 8.48 + 6.09 + 72.7 = 87.7
88 ( 0.8258) = 72.7
2.41
The electrons surrounding a nucleus have specific energies. Electrons with similar energies will
be found grouped together within a specific energy level.
2.42
The first energy level is filled with two electrons. The second energy level can hold a maximum
of eight electrons. Because we are only considering the first twenty elements, the third energy
level will have eight electrons present and the fourth energy level will have only two electrons in
it.
2.43
a. 8
b. 5
c. 8
d. 0
e. 8
2.44
a. zero
b. six
c. five
d. eight
e. zero
2.45
a. 2, 4
b. 2, 8, 8
c. 2, 8, 6
d. 2, 8, 4
e. 2, 8, 3
f. 2, 5
2.46
a. 2, 8, 5
b. 2, 8
c. 2, 6
d. 2, 8, 8
e. 2, 8, 3
f. 2, 8, 4
2.47
a. Li
b. Mg
c. H
d. Cl
e. O
2.48
a. N
b. S
c. C
d. Ar
e. Al
2.49
a. gain
b. emit
2.50
a. X-rays have higher energies than microwaves and radio waves.
b. We shield ourselves from unnecessary exposure to x-rays because our tissues are damaged by
high energies.
Chapter 2 Answers and Solutions
2.51
a. boron: 2, 3
aluminum: 2, 8, 3
b. Three
c. Group 3A (3)
2.52
a. fluorine: 2, 7 chlorine: 2, 8, 7
b. Seven
c. Group 7
2.53
a. 2 e−, Group 2A (2)
d. 5 e−, Group 5 A (5)
a. 1 e-, Group 1A (1)
d. 8 e-, Group 8A (18)
2.54
b. 7 e−, Group 7A (17)
e. 2 e−, Group 2A (2)
b. 4 e-, Group 4A (4)
e. 4 e-, Group 4A (4)
c. 6 e−, Group 6A (16)
f. 7 e−, Group 7A (17)
c. 8 e-, Group 8A (18)
f. 1 e-, Group 1A (1)
2.55
Mg, Ca, and Sr have similar properties because they are members of the same group (family) in
the periodic table. Chemical properties are related to the number of electrons in the outermost
occupied energy level, and these three elements all have two electrons in their outermost shell.
2.56
Bromine and iodine (you could also have selected fluorine or astatine) would exhibit physical
and chemical properties similar to chlorine.
2.57
An s subshell holds up to 2 electrons, a p subshell up to 6 electrons, a d subshell up to10
electrons, and an f subshell up to 14 electrons. An orbital holds up to two electrons. There is one
orbital in an s subshell, 3 orbitals in a p subshell, 5 orbitals in a d subshell, and 7
orbitals in a f subshell.
a. 2 electrons (orbital)
b. 6 electrons
c. 10 (s + p)
d. 2 electrons
2.58
a. 2 electrons
2.59
b. 1s2 2s2 2p6 3s2 3p3
c. 1s2 2s2 2p6 3s2 3p6
a. 1s2 2s2 2p6 3s2
2
2
6
2
4
2
2
6
2
5
d. 1s 2s 2p 3s 3p
e. 1s 2s 2p 3s 3p
f. 1s2 2s2 2p6 3s2 3p6 4s2 3d10
2
2
6
2
6
2
10
6
2
2
2
6
2
g. 1s 2s 2p 3s 3p 4s 3d 4p 5s
h. 1s 2s 2p 3s 3p6 4s2 3d10 4p6 5s2 4d10 5p5
2.60
a. 1s2 2s2 2p6 3s2 3p6 4s1
b. 1s2 2s2 2p6 3s1
c. 1s2 2s2
d. 1s2 2s2 2p3
2
2
2
2
2
6
2
6
2
2
2
6
f. 1s 2s 2p 3s 3p 4s g. 1s 2s 2p 3s2 3p6 4s2 3d5
e. 1s 2s 2p
h. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
2.61
a. hydrogen (H)
d. neon (Ne)
b. nitrogen (N)
e. silicon (Si)
c. sodium (Na)
f. bromine (Br)
2.62
a. carbon (C)
d. calcium (Ca)
b. lithium (Li)
e. sulfur (S)
c. sulfur (S)
f. strontium (Sr)
2.63
Any element with a two-letter symbol has the first letter capitalized and the second letter in
lower case. CO would indicate a compound made of the two elements carbon and oxygen.
2.64
a. Incorrect. The symbol for copper is Cu
c. Correct as written
e. Incorrect. The symbol for potassium is K
g. Correct as written
b. Incorrect. The symbol for silicon is Si.
d. Incorrect. The symbol for fluorine is F.
f. Correct as written
h. Incorrect. The symbol for lead is Pb.
2.65
a. Mg, magnesium
b. Br, bromine
c. Al, aluminum d. O, oxygen
2.66
a. Group 1, period 4
b. Group 5, period 3
c. Group 4, period 2
2.67
a. The proton is a positive particle.
b. Electrons are found outside of the nucleus.
c. The nucleus is the smallest part of the atom. d. The electron has a negative charge.
e. Most of the mass of the atom is due to its protons and neutrons.
2.68
a. 1 proton, 1 neutron
c. 48 protons, 58 neutrons
b. 2 electrons
c. 18 (s + p + d)
d. 2 electrons
d. Group 8, period 8
b. 17 protons, 20 neutrons
d. 83 protons, 126 neutrons
Atoms and Elements
2.69
a. 26 protons, 30 neutrons, 26 electrons
b.
51
c. 51Cr
Fe
26
24
2.70
No. The atomic mass is the weighted average of the eight naturally occurring isotopic masses.
2.71
a. Atoms are the smallest particles of an element that retain the properties of that element.
Isotopes are atoms of an element with a specific mass number (specific number of neutrons).
b. The atomic number indicates the number of protons found in the nucleus of an atom. (It is also
equal to the number of electrons present in a neutral atom.) The mass number indicates the
total number of particles (protons plus neutrons) present in the nucleus of a particular atom.
2.72
a. An elemental symbol is the unique one- or two-letter shorthand notation used for each element
found on the periodic table. An atomic symbol specifies a single isotope of an element.
b. The atomic number indicates the number of protons found in the nucleus of an atom. (It is also
equal to the number of electrons present in a neutral atom.) Atomic mass is the actual mass of
a particular isotope of an element.
2.73
a. 16X
17
8
8
b. 16X
17
8
8
c. 16X
16
8
9
18
X
10
d. 16X
8
2.74
18
X
18
X
All have 8 protons
X
All are isotopes of oxygen
8
X
18
8
X
Mass number of 16
X
Mass number of 18
X
Both have 8 neutrons
8
18
10
a. 64Zn
66
30
30
Zn
67
68
70
30
30
30
Zn
Zn
Zn
b. All of these isotopes contain 30 protons and 30 electrons. Zinc-64 contains 34 neutrons,
Zinc-66 contains 36 neutrons, Zinc-67 contains 37 neutrons, Zinc-68 contains 38 neutrons,
and Zinc-70 contains 40 neutrons.
2.75
Portion of mass due to copper-63: (63 amu ✕ 0.692) = 43.6 amu
Portion of mass due to copper-65: (65 amu ✕ 0.308) = 20.0 amu
Adding these numbers yields the weighted average atomic mass for copper:
43.5 + 20.0 = 63.6 amu
2.76
Portion of mass due to Magnesium-24: (24 amu ✕ 0.790) = [ 18.96 ] → 19.0 amu
Portion of mass due to Magnesium-25: (25 amu ✕ 0.100) = [ 2.5 ] → 2.50 amu
Portion of mass due to Magnesium-26: (26 amu ✕ 0.110) = [ 2.86 ] → 2.86 amu
Adding the numbers gives the weighted average atomic mass of magnesium:
19.0 + 2.50 + 2.86 = 24.4 amu
2.77
1 in. ✕ 2.54 cm ✕
1 in.
1 atom
= 8.09 ✕ 107 atoms
3.14 x 10−8 cm
2.78
2.00 cc ✕ 11.3 g ✕
1 cc
1 atom
3.4 x 10-22 g
2.79
Any two of the following in each part are correct responses:
a. helium, beryllium, magnesium, calcium, strontium, barium, and radium
b. oxygen, sulfur, selenium, tellurium, and polonium
c. neon, argon, krypton, xenon, and radon
d. boron, aluminum, gallium, indium, and thallium
= 6.6 x 1022 atoms
Chapter 2 Answers and Solutions
2.80
a. Atomic mass is the actual mass of a particular isotope of an element. The average atomic
mass is the weighted average of all naturally occurring isotopic masses.
b. Atoms are the smallest particles of an element that retain the properties of that element. A
nucleus is the very small region within an atom which contains all of that atom’s protons and
neutrons.
2.81
Any two of the following in each part are correct responses:
a. fluorine, chlorine, bromine, iodine, and astatine
b. helium, neon, argon, krypton, xenon, and radon
c. lithium, sodium, potassium, rubidium, cesium, and francium
d. beryllium, magnesium, calcium, strontium, barium, and radium
2.82
a. metal
e. metal
b. metal
f. nonmetal
c. metal
g. metal
d. nonmetal
h. metal
2.83
a. 3
b. 3
c. 10
d. 2
2.85
a. Ga, gallium
d. Ti, titanium
b. C, carbon
e. Kr, krypton
2.86
a. phosphorus
d. gallium
b. sulfur
e. radium
2.87
a. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p3or [Ar] 4s2 3d10 4p3
b. 1 s2 2s22p6 3s2 3p6 4s2 3d10 4p6 5s1 or [Kr] 5s1
c. 1s 2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 or [Xe] 6s2
d. 1s2 2s2 2p6 3s2 3p2 or [Ne] 3s2 3p2
e. 1s 2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
or [Ar] 4s2 3d10 4p5
2.88
a. F, fluorine
d. Ar, argon
b. Al, aluminum
e. Cd, cadmium
c. Rb, rubidium
c. indium
f. potassium
c. Fe, iron
f. Cs, cesium