Question

Define atomicity and molecular mass​

Answer 1

1. Atomicity is defined as the total number of atoms present in a molecule. For example, each molecule of oxygen is composed of two oxygen atoms. So atomicity of oxygen is 2. In older contexts, atomicity is sometimes used in the same sense as valency.
2. The molecular mass (m) is the mass of a given molecule: it is measured in daltons (Da or u). ... The molecular mass and relative molecular mass are distinct from but related to the molar mass. The molar mass is defined as the mass of a given substance divided by the amount of a substance and is expressed in g/mol.