Question

some atoms are exceptions to the octet rule by having an expanded octet. which characteristic is needed for an atom to have an expanded octet? the atom has empty d - orbitals. the atom has more than eight valence electrons before bonding. the atom has empty p - orbitals. the atom has fewer than eight valence electrons after bonding.

Explanation:

原子要形成扩展八隅体，需要有空的d轨道来容纳更多电子。p轨道一般不能使原子形成扩展八隅体；原子在成键前不会有超过8个价电子；成键后价电子数少于8个与扩展八隅体无关。

Answer:

The atom has empty d - orbitals.