the number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table.

The mass of an atom of a chemical element expressed in atomic mass units.

the total number of protons and neutrons in a nucleus.

a particle smaller than an atom

where electrons are when they go around the nucleus of an atom.

the fixed amount of energy that a system described by quantum mechanics, such as a molecule

an outer shell electron that is associated with an atom

thermodynamic stability of a chemical system.

chemical substance tends to undergo a chemical reaction in time.

substance in which electrical charge carriers, usually electrons.

a thing or substance used for insulation

solid substance that has a conductivity between that of an insulator and that of most metals