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:

Atoms with expanded octets (more than 8 electrons around the central atom in a molecule) need empty d - orbitals. For example, in \(SF_6\), sulfur (S) has empty 3d orbitals. The octet rule is based on the filling of s and p orbitals (a total of 8 electrons: \(2s + 6p\)). But when there are empty d orbitals, more electrons can be accommodated.

• Atoms do not have more than 8 valence electrons before bonding (violates basic electron - filling rules for ground - state atoms).
• Empty p - orbitals do not contribute to an expanded octet (p - orbitals can hold a maximum of 6 electrons, and the octet rule already considers s and p orbitals).
• Having fewer than 8 valence electrons after bonding is related to incomplete octets (e.g., \(BF_3\)), not expanded octets.

Answer:

The atom has empty d - orbitals.