By Mara Pesacreta
Updated Aug 30, 2022
A compound is a chemical species formed by two or more elements bound together by chemical bonds. Separating a compound requires chemical reactions. Knowing the elemental ratios within a compound enables precise quantification of each component and aids in interpreting reaction stoichiometry. Connecting unit measurements to the way elements assemble into compounds deepens comprehension of these ratios.
Interpret the coefficients. A coefficient precedes a chemical formula to indicate the number of molecules (or moles) of that species. If omitted, the coefficient is one. For example, 2NO₂ denotes two moles of nitrogen dioxide.
Decode the subscripts. Subscripts (small numbers to the lower right of an element symbol) specify the number of atoms of that element in one molecule. A subscript of one is omitted. In NO₂, one nitrogen atom and two oxygen atoms are present per molecule.
Express each element’s mole count relative to the compound. Divide the moles of an element by the moles of the compound. For 2NO₂, nitrogen’s ratio is 1 : 2 (one mole of N per two moles of NO₂) and oxygen’s ratio is 2 : 2 (two moles of O per two moles of NO₂).
Compare the elemental ratios. By reviewing the ratios, you can identify which element is more abundant. In 2NO₂, nitrogen is present at 1 : 2 relative to oxygen, so oxygen is twice as plentiful.
