Stability of Atoms in 3p

[Rajshree 1F]

I always understood the octet rule where the atom is most stable in that form. However, after learning about d-orbitals and exceptions to the octet rules, do these atoms have a different number that is the most stable or does it work differently?

[Jay Solanki 3A]

Hey!

So it is not exactly a specific number that makes it more stable, but it depends on the electron configurations of the atom and the specific compound. For instance, in PCl5, the P atom becomes the most stable when it has 5 bonded pairs since that best lowers the formal charge of the phosphorus atom. However, in the phosphate ion PO4^3-, you would have to interpret the various resonance structures to observe which model best lowers the formal charge. It may be one in which Phosphorus has more than 8 electrons or it may be a structure where phosphorus only has an octet, but the entire molecular structure relies on keeping the formal charge as low as possible. Hope this helps!

[Kathy_Li_1H]

Hi! I don't believe there is a specific numerical value that ensures stability within atoms but I believe it is based on whether the orbitals are filled, if they have 8 valence electrons, and minimizing the amount of formal charge.

[Katherine_Douglas_1F]

It's not so much the number of electrons that make the molecule more or less stable but the formal charge. For a lot of atoms, this happens to be 8 valence electrons in different configurations of bonded pairs and lone pairs.