Atomic mass class 9 science
Atomic mass refers to the mass of a single atom, and it’s primarily determined by the combined mass of protons and neutrons in an atom’s nucleus (since electrons have negligible mass in comparison). It is measured in atomic mass units (amu).
The atomic mass is often close to the mass number, which is the sum of protons and neutrons.
Since elements often have isotopes the average atomic mass of an element is calculated by considering the relative abundance of its isotopes.