hypervalence

Hypervalence refers to compounds where a central atom is bonded to more atoms than an octet of electrons would allow. This means the central atom accommodates more than eight electrons in its valence shell, such as 10, 12, or even 16 electrons. Hypervalent compounds are common and generally as stable as those that follow the octet rule. This phenomenon is rare in the first two periods of the periodic table but common from the third period onward. While the availability of d orbitals in elements from the third period and beyond is often cited as an explanation, quantum mechanical theories suggest hypervalence might be more of a steric effect, where larger atoms can accommodate more surrounding atoms. Examples include sulfur hexafluoride (SF₆), which has 12 electrons around the sulfur atom. Organosulfur compounds like sulfuranes (SR₄) and persulfuranes (SR₆) are also examples of hypervalent species.12