polyatomic ions are often said to be a cross between covalent compounds and ionic compounds why can they be...

Question

polyatomic ions are often said to be a cross between covalent compounds and ionic compounds why can they be characterized in such a way???

Answer 1

Polyatomic ions are held together by the bonds between their elements. Those bonds are stronger than the bonds formed between the other ions they bond with. So in many chemical reactions the poly atomic ions stay bonded together, moving as a complete entity.

Example Ca(NO3)2 + 1[2(NH4)(SO4)] => 2 (NH4)(NO3) + Ca(SO4)

Each of those polyatomic ions stayed bonded together and physically rearrange during the reaction.

It is as if their bonds were covalent, even though electronegativity might predict that their bonds should be ionic (like the electronegativity difference for NH4).