Question

How many double bonds are present in the 'best' resonance structure of the phosphate ion?

A. 0
B. 1
C. 2
D. 4

Answer 1

The best resonance structure of the phosphate ion has two double bonds.

Step-by-step explanation:

The best resonance structure of the phosphate ion has two double bonds. In the phosphate ion, there is a central phosphorus atom bonded to four oxygen atoms. One of the oxygen atoms must have a double bond to phosphorus to complete the octet on the central atom. However, all oxygen atoms are equivalent, so the double bond could form from any one of the three oxygen atoms. This gives rise to three resonance forms of the phosphate ion, but the best structure has two double bonds.

Answer 2

The phosphate ion (\(PO_4^{3-}\)) has resonance structures, and the 'best' resonance structure is the one that minimizes formal charges. In the resonance structures of the phosphate ion, there are double bonds involving oxygen atoms.

The correct answer is:

C. 2

There are two double bonds present in the 'best' resonance structure of the phosphate ion.