Atomic Mass: Atomic mass refers to the mass of an atom of a specific chemical element. It is typically expressed in atomic mass units (u) or Daltons (Da). Atomic mass takes into account the combined masses of protons, neutrons, and electrons in an atom.
Relative Atomic Mass: Relative atomic mass (also known as atomic weight) is a dimensionless quantity that represents the average mass of an atom of an element relative to 1/12th the mass of a carbon-12 atom. It is calculated by considering the abundance of isotopes of an element and their respective masses. The relative atomic mass is often expressed as a decimal number.
Standard Atomic Weight: Standard atomic weight is a specific value assigned to an element's relative atomic mass. It is the average relative atomic mass of an element based on the isotopic composition of naturally occurring elements on Earth. Standard atomic weights are typically provided on the periodic table and serve as a reference for calculations involving chemical reactions and measurements. The values of standard atomic weights may be periodically updated as more precise measurements are made.
In summary, atomic mass refers to the mass of a single atom, relative atomic mass represents the average mass of an atom of an element relative to carbon-12, and standard atomic weight is the specific value assigned to an element's relative atomic mass based on the isotopic composition of naturally occurring elements.