The terms "relative atomic mass" and "atomic mass" are often used interchangeably, but in some contexts, they can have slightly different meanings. Here's how they are commonly understood:
Relative Atomic Mass: Relative atomic mass refers to the mass of an atom of a specific element relative to a standard reference value. It is a dimensionless quantity that compares the mass of an atom to a reference standard. The reference standard is usually based on the mass of a carbon-12 atom, which is defined as exactly 12 atomic mass units (u) or unified atomic mass units (u).
The relative atomic mass is calculated by comparing the mass of an atom to the mass of a carbon-12 atom on a scale where carbon-12 is assigned a relative atomic mass of exactly 12 u. For example, if the relative atomic mass of an element is 14 u, it means that an atom of that element is approximately 1.17 times heavier than a carbon-12 atom.
Atomic Mass: Atomic mass, sometimes referred to as atomic weight, is a more general term that can have different interpretations depending on the context.
In one context, atomic mass is used synonymously with relative atomic mass. It represents the average mass of an atom of a specific element relative to the standard reference value, which is the mass of a carbon-12 atom.
In another context, atomic mass can refer to the actual, absolute mass of an atom in atomic mass units (u) or kilograms (kg). In this sense, atomic mass is not relative to any particular standard and represents the actual mass of an atom. The absolute atomic mass can be measured using techniques such as mass spectrometry.
It's important to note that in most cases, when the term "atomic mass" is used without further specification, it usually refers to the relative atomic mass.
In summary, relative atomic mass and atomic mass are often used interchangeably, but "relative atomic mass" specifically refers to the mass of an atom of an element relative to a standard reference value, while "atomic mass" can refer to either the relative atomic mass or the absolute mass of an atom.