Question

What is the allotrope of phosphorus in which P-atom completes its octet?

(a) Alpha-black phosphorus

(b) Beta-black phosphorus

(c) White phosphorus

(d) Red phosphorus

The question was asked in an online interview.

Enquiry is from P-Block Elements in chapter P-Block Elements of Chemistry – Class 12

Answer 1

Right answer is (c) White phosphorus

The explanation is: White phosphorus exists as P4 units. The four sp^3 hybridized phosphorus atoms lie at the corners of a regular tetrahedron with an angle of 60 degree. Each phosphorus atom is linked to three other P-atoms by covalent bonds so that each p-atom completes it octet.