Formation of Molecular Orbitals — Prelims Questions

Which of the following statements about the formation of molecular orbitals is INCORRECT?

Which of the following diatomic species has a bond order of 2.5?

Which of the following species is diamagnetic?

Which of the following pairs of atomic orbitals cannot combine to form a molecular orbital?

Which of the following statements correctly describes a bonding molecular orbital?

What is the bond order of the $He_2^+$ ion?

Which of the following statements regarding the stability of molecular species is TRUE?