Which molecule would you predict would be more stable: be2 - 2 or be2?

C2^2 + will or will not exist?

Because of sp mixing Ď3> Ď€1; assume Ď*2 antibonding that is not always the case (can be approximately nonbonding):

C2^2 + = 6e - Ď1 (2e-) Ď*2 (2e-) Ď€1 (2e-) Ď3 (0e-) Ď€2 * (0e-) Ď4 (0e-) *

Bond Order (bo) = [ÎŁ (bonding e-) - ÎŁ (antibonding e-) ]/2

= [4 (Ď1 (2e-) Ď€1 (2e-)) - 2 (Ď*2 (2e-)) ] = 1

So it is bonding and predicted to exist.

b. Li2 will or will not exist?

(cf H2!) Li2 = 2e Ď1 (2e-) Ď*2 (0e-) bo = 1; should (and does) exist

c. Be2^2 + will or will not exist?

Be2^2 + = 2e Ď1 (2e-) Ď*2 (0e-) bo = 1; should exist

d. Li2^2 - will or will not exist?

Li2^2 - 4e - Ď1 (2e-) Ď*2 (2e-) bo = 0; will not exist