Definitions

• What is a positive ion? (Cation)

  an atom that has lost electrons
• What is a negative ion (anions)

  an atom that has gained electrons
• Atomic number

  the number of protons (proton number) in the nucleus
• mass number

  number of protons and neutrons combined
• isotope

  atoms with the same number of protons but a different number of neutrons
• ionisation energy

  the amount of energy required to remove one mole of electrons from one mole of atoms, in the gaseous state
• successive ionisation energy

  series of ionisation energies