Expanded octet is possible for which rows or below?

Expanded octet is possible for which rows or below?

• A. First Row Only
• B. Second Row Only
• C. Third Row and Below
• D. All Rows

Answer: (C)

Expanded octet means more than eight electrons around a central atom. That can happen only when the valence shell has access to additional orbitals, traditionally the 3d (and higher) orbitals. That capability starts with elements in the third row and continues for all heavier elements, because they have available d orbitals to accommodate extra electron density from bonds. In contrast, the first and second rows don’t have accessible d orbitals in their valence shells, so they typically cannot exceed eight electrons around the central atom. Therefore, expanded octet is possible from the third row and all rows below it.

Expanded octet means more than eight electrons around a central atom. That can happen only when the valence shell has access to additional orbitals, traditionally the 3d (and higher) orbitals. That capability starts with elements in the third row and continues for all heavier elements, because they have available d orbitals to accommodate extra electron density from bonds. In contrast, the first and second rows don’t have accessible d orbitals in their valence shells, so they typically cannot exceed eight electrons around the central atom. Therefore, expanded octet is possible from the third row and all rows below it.