Ions

• Ions are atoms that have an unequal amount of protons and electrons. When atoms are ionic, they have a net charge.
• Ions can be positively charged or negatively charged.
• When atoms have no net charge, they are not ionic. (requires review)

Cations and Anions

• Cations are positively charged ions, with the atom having more protons than electrons.
• Anions are negatively charged ions, with the atom having more electrons than protons.

Formation of Ions

• Atoms will lose or gain electrons to get a full valence shell. (See here for a basic rundown of a valence shell.)
• There are specific groups in the periodic table that are able to achieve a full outer shell through different methods.
  • Group 1 and 2
    • 1 or 2 electrons in valence shell
    • Lose electrons for full outer shell
    • = Cations
  • Group 16 and 17
    • 6 or 7 electrons in valence shell
    • Gain electrons for full outer shell
    • = Anions
  • Group 13 (Aluminium only)
    • Lose three valence electrons for $A{l}^{3+}$
  • Some groups of the periodic table are not ionic, such as Group 18.

Ionic Bonding