The terms "atomic mass," "relative atomic mass," and "atomic weight" are related but not exactly interchangeable. They refer to slightly different concepts:
Atomic Mass: Atomic mass refers to the mass of an atom, typically expressed in atomic mass units (amu) or unified atomic mass units (u). It can be specifically used to describe the mass of an individual atom or the average mass of atoms of a particular element.
Relative Atomic Mass: Relative atomic mass (also known as atomic mass or atomic weight) is the average mass of atoms of an element compared to 1/12th the mass of a carbon-12 atom. It is a dimensionless quantity and is often represented by the symbol "Ar" or "Aᵣ". Relative atomic mass takes into account the different isotopes of an element and their abundances.
Atomic Weight: Atomic weight is another term used to describe the average mass of atoms of an element, similar to relative atomic mass. In the past, atomic weight was commonly used, but now the preferred term is relative atomic mass. The atomic weight of an element is determined by the average mass of its isotopes and their relative abundances.
While these terms are related, "atomic mass" specifically refers to the mass of an atom, "relative atomic mass" emphasizes the comparison to carbon-12, and "atomic weight" is an older term that is often used interchangeably with relative atomic mass. The specific term used may depend on the context or the scientific literature being referenced.