Octet rule

[Shaniya Kerns 4D]

What is the octet rule and which elements do not apply. Why can SO2 have 2 double bonds and 2 lone pairs attached to S but is not allowed to have 2 triple bonds and no lone pairs?

[805909756]

The octet rule states that atoms tend to form compounds in ways that give them eight valence electrons, and thus the electron configuration of a noble gas. An exception to an octet of electrons is in the case of the first noble gas, helium, which only has two valence electrons. There are exceptions to only having eight electrons, including how elements in the third period and beyond (such as phosphorus, sulfur, chlorine, and heavier elements) can accommodate more than eight electrons in their valence shells due to the availability of d orbitals.

For SO2, if you were to have two triple bonds in SO2, the formal charges on the oxygen atoms would be more significant, and the structure would have a higher energy, and therefore less stable. The Lewis structure with two double bonds and two lone pairs on sulfur gives a more stable and reasonable representation of the molecule, satisfying the octet rule for oxygen while allowing sulfur to have an expanded octet and overall creating a more stable structure.