Question

Question #7f0a7

Answer 1

Phosphoric acid, or `H_3PO_4`, has a total of 32 valence electrons, 5 from the phosphorus atom, 6 from each of the four oxygen atoms, and 3 from each of the hydrogen atoms.

The Lewis structure of phosphoric acid looks like this:

The phosphorus atom has zero lone pairs, and uses all its five valence electrons to form bonds with the four oxygen atoms - 3 single bonds and 1 double bond.

As you can see, the five bonds it forms give phosphorus a total of 10 electrons in its valence shell, which implies that it does not obey the octet rule.

However, because phosphorus is located in period 3 of the periodic table, it can use its d-orbitals to accomodate more than 8 electrons in its valence shell.