The terms "atomic mass" and "relative atomic mass" are often used interchangeably, but they can have slightly different meanings depending on the context. Here's an explanation of both terms:
Atomic Mass: Atomic mass refers to the mass of an atom. It represents the total mass of protons, neutrons, and electrons in an atom. However, since the mass of electrons is extremely small compared to protons and neutrons, it is usually neglected when calculating atomic mass. Atomic mass is typically expressed in atomic mass units (amu) or unified atomic mass units (u).
Relative Atomic Mass: Relative atomic mass, also known as atomic weight, is the average mass of all the naturally occurring isotopes of an element relative to the mass of an atom of carbon-12. Since most elements have multiple isotopes with different masses, the relative atomic mass takes into account the abundance of each isotope in nature.
The relative atomic mass is calculated by taking the weighted average of the masses of all the isotopes, where the weighting factor is the abundance of each isotope. This value is dimensionless and is often reported as a decimal number on the periodic table. The relative atomic mass can differ slightly from the atomic mass due to the inclusion of isotopes and their respective abundances.
In summary, atomic mass refers to the total mass of an atom, while relative atomic mass represents the average mass of all the isotopes of an element, taking into account their abundances.