相对式量Relative formula mass

相对式量 Mr 是化学式中各原子相对原子质量的总和，没有单位。对于离子化合物和巨型结构，按式单位计算，称为相对式量；对于分子化合物也叫相对分子质量。其数值与摩尔质量（g mol⁻¹）相同。

Relative formula mass, Mr, is the sum of the relative atomic masses of all the atoms in a formula and has no unit. For ionic compounds and giant structures it is worked out per formula unit; for molecular substances it is also called relative molecular mass. It is numerically equal to the molar mass in g mol⁻¹.