Expanded valence shells

[Tracy Tolentino_2E]

So according to Professor Lavelle, atoms in period 3 or higher have d-orbitals in valence shell that can accommodate additional electrons. Does that mean all the elements from period 3 onward are exceptions to this octet rule? And can someone explain the phosphorus pentachloride example? How does phosphorus have 10 valence electrons?

[Maya Gollamudi 1G]

Yes, elements from period 3 onwards will have expanded valence shells because the octet rule applies only to the s and p blocks of the periodic table.

In PCl5, P forms five bonds (10 shared electrons) as it is bonded to 5 atoms of Cl.

[Petrina Kan 2I]

I was also wondering the same thing. Is it just P, S, and Cl or is it all the elements in the periods below (including Ga, Ge, etc.) that follow this expanded valence shell rule?

[805097738]

how do you know how many valence electrons atoms in the d block have