34.

(a) The number of different m

l

s is 2l + 1 = 3, and the number of different m

s

s is 2. Thus, the number

of combinations is N = (3

× 2)

2

/2 = 18.

(b) There are six states disallowed bythe exclusion principle, in which both electrons share the quantum

numbers

(n, l, m

l

, m

s

) =

2, 1, 1,

1

2



,

2, 1, 1,

−

1

2



,

2, 1, 0,

1

2



,

2, 1, 0,

−

1

2



,

2, 1,

−1,

1

2



,

2, 1,

−1, −

1

2



.