State octet rule in chemistry

Question

Explain what is octet rule in chemistry?

Answer 1

Octet rule is a simple chemical rule of thumb which states that the atoms incline to combine in a way that they have eight electrons in their valence shells, giving them the similar electronic configuration as noble gas. This 8-electron configuration is particularly stable for the reason that with 8 valence electrons, s- and p-orbitals are completely filled (with 2 in s-orbital, and 6 in p-orbitals). Containing completely filled orbitals offers increased stability due to something named "exchange energy".
Octet rule is appropriate to the main-group elements, particularly nitrogen, carbon, the halogens and oxygen, but also metals in the first two columns of a periodic table (but not to the conversion metals in middle of periodic table). Reminde that elements hydrogen (H) and helium (He) don’t follow the octet rule, rather the "duet" rule (2 electrons) because they don’t have any p-orbital electrons.