Question

what do you mean by divalent polyatomic anion

Answer 1

the polyayomic anions are those ions which have more 1 valency is known as divalent polyatomic anion.
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Answer 2

A polyatomic ion, also known as a molecular ion, is a charged chemical species (ion) composed of two or more atoms covalently bonded or of a metal complex that can be considered to be acting as a single unit. The prefix poly- means "many," in Greek, but even ions of two atoms are commonly referred to as polyatomic.

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