Question

which of the following can easily form an ionic bond with a cation?
sr
ne
nh₄⁺
po₄³⁻

Explanation:

An ionic bond forms between a cation (positively - charged ion) and an anion (negatively - charged ion). Sr is a metal, Ne is a noble gas, and $NH_4^+$ is a cation. $PO_4^{3 - }$ is an anion and can form an ionic bond with a cation.

Answer:

D. $PO_4^{3 - }$