Question

Which statement is not true of molecular orbitals?

A)The number of molecular orbitals formed is always equal to the number of atomic orbitals combined.

B)A molecular orbital can accommodate up to two electrons.

C)When electrons are added to orbitals of the same energy, the most stable arrangement is predicted by Hund's rule.

D)Low-energy molecular orbitals fill before high-energy molecular orbitals fill.

E)Antibonding molecular orbitals are higher in energy than all of the bonding molecular orbital

Answer 1

the postulates of MO theory

• The bond formatuon takes place between the molecule atomic orbitals of similar symmetry,similar energy overlap along the nuclear axis .
• Molecular orbital theory assumes the wave nature of electrons ,thus during the overlapping the wave functions of different atoms interact in two ways- Destructive interference and constructive intereference.
• The molecules possesing higher number of bonding electrons are more stable.
• The number of molecular orbitals formed must be equal to the number of orbitals overlapped.
• The filling of electrons in these molecular orbitals takes place in increasing order of energy acc. To Aufbau’s rule.
• Any orbital will possess max. Two electrons acc. To Pauli’s exclusion principle.
• In degenerating orbitals pairing of electrons will take place acc. To Hund’s rule
• If all the electrons are paired in a molecule,then it is diamagnetic while if even one is unpaired then it is paramagnetic in nature

answer is E . because not always antibonding mos are high in energy than bonding MOs . Antibonding orbitals will be in hgher in energy than corresponding bonding Mos.and lower energy orbitals