Classify the following functions as symmetric, antisymmetric, or neither in the exchange of electrons 1 and 2:

a. [1s (1) 2s (2) + 2s (1) 1s (2)] [α (1) β (2) − β (1) α (2)]

b. [1s (1) 2s (2) + 2s (1) 1s (2)] α (1) α (2)

c. [1s (1) 2s (2) + 2s (1) 1s (2)] [α (1) β (2) + β (1) α (2)]

d. [1s (1) 2s (2) − 2s (1) 1s (2)] [α (1) β (2) + β (1) α (2)]

e. [1s (1) 2s (2) + 2s (1) 1s (2)] [α (1) β (2) − β (1) α (2) +α (1) α.