CHEMISTRY 201X
October 1-5, 2007
Practice Problems
(57)
Which of the following combinations of quantum numbers are allowed for an electron in
a one-electron atom?
Which are not?
(a)
n
= 2,
l
= 2,
m
= 1,
m
s
= 1/2
Not allowed: for
n
= 2, can only have
l
= 0, 1.
(b)
n
= 3,
l
= 1,
m
= 0,
m
s
=
−
1/2
Allowed
(c)
n
= 5,
l
= 1,
m
= 2,
m
s
= 1/2
Not allowed: for
l
= 1, can only have
m
= +1, 0 or
−
1.
(d)
n
= 4,
l
=
−
1,
m
= 0,
m
s
= 1/2
Not allowed: cannot have negative
l
numbers.
(e)
n
= 3,
l
= 2,
m
= 1,
m
s
= 0
Not allowed:
m
s
= +1/2 or
−
1/2 only, not 0.
(f)
n
= 2,
l
= 0,
m
= 1,
m
s
=
−
1/2
Not allowed: for
l
= 0, can only have
m
= 0.
(g)
n
= 7,
l
= 2,
m
=
−
2,
m
s
= 1/2
Allowed.
(h)
n
= 3,
l
=
−
3,
m
= 0,
m
s
=
−
1/2
Not allowed: cannot have negative
l
numbers.
(58)
Write down the ground state electronic configurations for
(a)
Elements: C, Se, Fe, P, Tc, Ho;
C:
[He](2
s
)
2
(2
p
)
2
2 unpaired electrons
Se:
[Ar](3
d
)
10
(4
s
)
2
(4
p
)
4
2 unpaired electrons
Fe:
[Ar](4
s