The atomic mass of an element depends on what?

The atomic mass of an element depends on the number of neutrons. Atoms with the same number of protons, but a different number of neutrons are called isotopes and they each have a slightly different atomic mass. So all in all, the average atomic mass depends on the weight of all the isotopes and how frequent each isotope occurs. 

Non metal is an element or substance that is not a metal metal is a solid material that is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivitymetalloid is an element (e.g., germanium or silicon) whose properties are intermediate between those of metals and solid nonmetals. they are electrical semiconductors.