Video Transcript
Which of the following atomic groups, also known as polyatomic ions, has a valence of two? (A) Hydroxide, (B) nitrate, (C) phosphate, or (D) sulfate.
The question mentions the valence of polyatomic ions. The valence of an element is the number of electrons an atom gains, loses, or shares when forming a bond during a chemical reaction. The question asks about the valence of polyatomic ions. Polyatomic ions are cations or anions that are made up of at least two different types of atoms.
We have been given the name of four polyatomic ions in the answer choices. The chemical formulas for hydroxide, nitrate, phosphate, and sulfate are OH‒, NO3‒, PO4 3‒, and SO4 2‒, respectively. The polyatomic ions have one overall charge, despite containing more than one atom. The valence is indicated by the ionic charges. As hydroxide and nitrate have charges of one minus, which is just written as minus, they both have a valence of one. As phosphate has a charge of three minus, it has a valence of three. And as sulfate has a charge of two minus, it has a valence of two.
Therefore, the polyatomic ion with a valence of two is (D), sulfate.
