CHAPTER 2
ATOMIC STRUCTURE AND INTERATOMIC BONDING
PROBLEM SOLUTIONS
2.1
(a)
When two or more atoms of an element have different atomic masses, each is termed an
isotope
.
(b)
The atomic weights of the elements ordinarily are not integers because:
(1) the atomic masses
of the atoms generally are not integers (except for
12
C), and (2) the atomic weight is taken as the
weighted average of the atomic masses of an atom's naturally occurring isotopes.
2.2
Atomic mass is the mass of an individual atom, whereas atomic weight is the average (weighted) of
the atomic masses of an atom's naturally occurring isotopes.
2.3
(a)
In order to determine the number of grams in one amu of material, appropriate manipulation of
the amu/atom, g/mol, and atom/mol relationships is all that is necessary, as
# g/amu =
1 mol
6.023 x 10
23
atoms
�
�
�
�
�
�
1 γ /μολ
1 αμυ /ατομ
�
�
�
�
�
�
= 1.66 x 10
24
g/amu
(b)
Since there are 453.6 g/lb
m
,
1 lb  mol = 453.6 g/lb
m
(
29
6.023ξ10
23
ατομσ/γ μολ
(
29
= 2.73 x 10
26
atoms/lbmol
2.4
(a)
Two important quantummechanical concepts associated with the Bohr model of the atom are
that electrons are particles moving in discrete orbitals, and electron energy is quantized into shells.
(b)
Two important refinements resulting from the wavemechanical atomic model are that electron
position is described in terms of a probability distribution, and electron energy is quantized into both
shells and subshellseach electron is characterized by four quantum numbers.
2.5
The
n
quantum number designates the electron shell.
2
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The
l
quantum number designates the electron subshell.
The
m
l
quantum number designates the number of electron states in each electron subshell.
The
m
s
quantum number designates the spin moment on each electron.
2.6
For the
L
state,
n
= 2, and eight electron states are possible.
Possible
l
values are 0 and 1, while
possible
m
l
values are 0 and ±1.
Therefore, for the
s
states, the quantum numbers are
200(
1
2
)
and
200(

1
2
)
. For the
p
states, the quantum numbers are 210(
1
2
) ,
210(

1
2
)
, 211(
1
2
) ,
211(

1
2
)
,
21(1)(
1
2
) , and
21(1)(

1
2
)
.
For the
M
state,
n
= 3, and 18 states are possible.
Possible
l
values are 0, 1, and 2;
possible
m
l
values are 0, ±1, and ±2; and possible
m
s
values are
±
1
2
. Therefore, for the
s
states,
the quantum numbers are 300(
1
2
) ,
300(

1
2
)
, for the
p
states they are 310(
1
2
) ,
310(

1
2
)
, 311(
1
2
) ,
311(

1
2
)
, 31(1)(
1
2
) , and
31(1)(

1
2
)
;
for the
d
states they are 320(
1
2
) ,
320(

1
2
)
, 321(
1
2
) ,
321(

1
2
)
,
32(1)(
1
2
)
,
32(1)(

1
2
)
, 322 (
1
2
) ,
322 (

1
2
)
, 32(2) (
1
2
) , and
32(2) (

1
2
)
.
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 Spring '06
 VanAntwerp
 Atom, Electron, 1s 2s

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