Question

In the correlation diagram for HF the molecular orbitals are formed by mixing the 1s on the hydrogen with a 2p orbital in fluorine because:

A) these orbitals have the same angular momentum

B) these orbitals have the same symmetry

C) these orbitals are closest in energy

D) a & b

E) all of the above

Answer 1

B) These orbitals have the same symmetry               Correct answer

1. Because of the effects of Zeff, orbital overlap between different kinds of atomic orbitals can occur here (e.g. 1s-2p overlap).
2. MO diagrams no longer look symmetric
3. For HF, the energy of the fluorine 2s orbital is below the 1s orbital energy of hydrogen (no mixing – doesn’t meet
energy requirement) 2p orbitals are closer to H 1s orbital energy – overlap can occur
4.Get two MO’s created between the H 1s orbital and the three F 2p orbitals (only one 2p orbital meets all three
requirements for forming MO with H 1s orbital)

Thank you.