What is a shorthand notation that represents a compound or diatomic molecule?

A shorthand notation that represents a compound or diatomic molecule is called a chemical formula. This notation uses symbols for the elements involved and subscripts to indicate the number of atoms of each element in the molecule. For diatomic molecules, such as oxygen (O₂) or nitrogen (N₂), the subscript "2" denotes that two atoms of the same element are bonded together. For compounds, like water (H₂O), the formula shows the ratio of different elements in the molecule.