Which of the following polyatomic ions will form an ionic compound with a single sodium ion? co32− po43− so42− no31−

A single sodium ion will combine due to its charge on it

Na^+

The single sodium ion has total one positive charge on it. so it requires only one electron or can bond to one negative charge

in the given polyatomic anions

a) CO3^-2 : it has two negative charge. So it will react with two sodium ions

it will forms Na2CO3

b) PO4^-3 :it has three negative charge. So it will react with three sodium ions

it will forms Na3PO4

c) SO4^-2 : it has two negative charge. So it will react with two sodium ions

it will forms Na2SO4

d) NO3^-1: it has one negative charge. So it will react with one sodium ion

it will forms NaNO3

Hence the correct answer is

Nitrate ion will react with single sodium ion as

Na+   + NO3-  ---> NaNO3