Period 3 elements can exceed the octet rule in which type of bonding?

• A. Ionic bonding
• B. Metallic bonding
• C. Covalent bonding that involves expanded octets
• D. Hydrogen bonding

Answer: (C)

Expanded octets happen in covalent bonding when a central period-3 element uses its available d-orbitals to accommodate more than eight electrons around it. In molecules like SF6 or PCl5, the central atom forms multiple covalent bonds and ends up surrounded by more than eight electrons (twelve in SF6, ten in PCl5). The key idea is that these atoms have access to additional orbitals beyond the basic s and p, allowing hypervalent structures. Ionic bonding transfers electrons to form ions with stable configurations and doesn’t rely on sharing enough electron pairs to expand the valence shell; metallic bonding involves delocalized electrons in a lattice and doesn’t center on a single atom with an expanded octet; hydrogen bonding is a dipole-dipole interaction between molecules and also doesn’t change the electron count around a specific atom.