Less than 8 electrons on an atom

[Sheik Sahadat]

Hello,
I understand that some atoms can have an expanded octet. We start seeing this concept at period 3 with phosphorus. However, how do we know which atoms can form a structure while having less than 8 electrons. Is there another trend for when this occurs? And if so, would the structure be more stable if the central atom had a full octet?
Thank you

[Mell Mercado 3F]

Atoms in period 3 and beyond can have expanded octets, but the trend is not strict. Elements like phosphorous, sulfur, and chlorine commonly exceed the octet rule due to the availability of d orbitals. The stability of a structure with less than 8 electrons on the central atom depends on factors like electronegativity and overall charge distribution, but getting a full octet is a more stable configuration.