Chemistry Reference
In-Depth Information
Table 4.3
Possible Sets of Quantum Numbers for the Last Eight Electrons of Argon
Quantum
Eleventh
Twelfth
Thirteenth
Fourteenth
Fifteenth
Sixteenth
Seventeenth
Eighteenth
Number
Electron
Electron
Electron
Electron
Electron
Electron
Electron
Electron
n
3
3
3
3
3
3
3
3
/
0
0
1
1
1
1
1
1
m
/
0
0
1
0
1
1
0
1
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
m
s
Solution
The sets are shown in Table 4.3. Note that the combination has
the same sum of
n
and as Because the sum is the same, the
combination with the lower
n
value is used for each of the thirteenth through
eighteenth electrons because it is lower in energy.
n
3,
/
1
/
n
4,
/
0.
When we try to add the nineteenth electron to write the configuration for
potassium (K), we encounter a new situation. The combination with the next
lowest sum of
n
and is The combination is higher
in energy. The nineteenth through twenty-first electrons can have the following
sets of quantum numbers:
/
n
4,
/
0.
n
3,
/
2
Quantum
Nineteenth
Twentieth
Twenty-first
number
electron
electron
electron
n
4
4
3
/
0
0
2
m
/
0
0
2
1
2
1
2
1
2
m
s
n
/
4
4
5
The fact that electrons having quantum number values and are
lower in energy than electrons with and is of extreme importance;
it explains the existence and position on the periodic table of the transition
metals. This point will be explained later.
n
4
/
0
n
3
/
2
EXAMPLE 4.10
Arrange the following electrons, identified only by their
n
and quantum num-
bers, in order of increasing energy from lowest to highest.
(a)
/
n
3,
/
2
(b)
n
5,
/
0
(c)
n
4,
/
2
(d)
n
4,
/
1
(e)
n
5,
/
1
Solution
Calculate the sum
n
/
for each electron:
(a)
n
3,
/
2,
so
n
/
5
(b)
n
5,
/
0,
so
n
/
5
(c)
n
4,
/
2,
so
n
/
6
(d)
n
4,
/
1,
so
n
/
5
(e)
n
5,
/
1,
so
n
/
6
