Question

What the covalencey of phosphorus atoms in excited state?

• A. $3$
• B. $4$
• C. $5$
• D. $1$

Answer 1

The correct option is C $5$

Phosphorus can have expanded octet, because it can shift it's lone pair electrons ($3s$ orbital electrons) to empty $3d$ obital during excited state and thus can form 5 bonds. So now there is 5 spaces along the singly filled orbitals to keep electrons or we may say that there can be 5 bonds now.