Electron energy level

All electrons that are in atoms are contained in discrete energy levels.

They’re in discrete energy levels, which means that they have to ‘snap’ to a specific energy levels - they have to be in one and can’t be in between levels.

The energy levels are relative to the nucleus of the atom, and we measure them in electronvolts. Each energy level is negative.

An isotope can have multiple different discrete energy levels, and together they make up an energy ladder.