Question

question 21 which statement is not true of molecular orbitals? the number of molecular orbitals formed is always equal to the number of atomic orbitals combined. a molecular orbital can accommodate up to two electrons. when electrons are added to orbitals of the same energy, the most stable arrangement is predicted by hunds rule. low - energy molecular orbitals fill before high - energy molecular orbitals fill. antibonding molecular orbitals are higher in energy than all of the bonding molecular orbitals.

Explanation:

1. In molecular orbital theory, the number of molecular orbitals formed is equal to the number of atomic orbitals combined, so the first statement is true.
2. According to the Pauli - exclusion principle, a molecular orbital can hold a maximum of two electrons with opposite spins, making the second statement true.
3. Hund's rule is used to predict the most stable electron - arrangement when electrons are added to degenerate (same - energy) orbitals, so the third statement is true.
4. Electrons fill molecular orbitals starting from the lowest - energy orbitals first, following the Aufbau principle, making the fourth statement true.
5. Antibonding molecular orbitals are higher in energy than bonding molecular orbitals, but not necessarily higher in energy than all bonding molecular orbitals in complex cases. For example, in some cases, the energy of a higher - lying bonding orbital can be higher than a lower - lying antibonding orbital. So the fifth statement is not always true.

Answer:

Antibonding molecular orbitals are higher in energy than all of the bonding molecular orbitals.