Question

the small number that comes after a chemical symbol or set of parentheses in a chemical formula; indicates the number of atoms or groups of atoms of the elements in one unit of the substance
superscript
yield
coefficient
subscript
a representation of a chemical reaction using numbers and symbols to indicate the substances and the number of units of each involved
balanced equation
chemical equation
coefficient
skeleton equation
a particle composed of two or more atoms joined together
ion
atom
electron
molecule

Explanation:

1. In a chemical formula, the small number after a chemical symbol or parentheses is a subscript which shows the number of atoms or atom - groups.
2. A chemical equation uses numbers and symbols to represent a chemical reaction and the amounts of substances involved. A balanced equation is a type of chemical equation with equal numbers of each atom on both sides.
3. A molecule is a particle made up of two or more atoms joined together.

Answer:

1. D. subscript
2. B. chemical equation
3. D. molecule