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Science

Ionic bonding

Ions are electrically charged particles formed when atoms [atom: All elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons. ] lose or gain electrons [electron: An electron is a very small negatively-charged particle found in an atom in the space surrounding the nucleus. ]. They have the same electronic structures as noble gases.

Metal atoms form positive ions, while non-metal atoms form negative ions. The strong electrostatic [electrostatic: An electrostatic force is generated by differences in electric charge (ie positive and negative) between two particles. It can also refer to electricity at rest. ] forces of attraction between oppositely charged ions are called ionic bonds.

Ions

How ions form

Ions are electrically charged particles formed when atoms lose or gain electrons [electron: An electron is a very small negatively-charged particle found in an atom in the space surrounding the nucleus. ]. This loss or gain leaves a complete highest energy level, so the electronic structure of an ion is the same as that of a noble gas - such as a helium, neon or argon.

Metal atoms and non-metal atoms go in opposite directions when they ionise:

  • Metal atoms lose the electron, or electrons, in their highest energy level and become positively charged ions
  • Non-metal atoms gain an electron, or electrons, from another atom to become negatively charged ions

Positively charged sodium and aluminium ions

Negatively charged oxide and chloride ions

How many charges?

There is a quick way to work out what the charge on an ion should be:

  • The number of charges on an ion formed by a metal is equal to the group number of the metal
  • The number of charges on an ion formed by a non-metal is equal to the group number minus eight
  • Hydrogen forms H+ ions.

 

 Group 1Group 2Group 3Group 4Group 5Group 6Group 7Group 0
Example elementNaMgAlCNOClHe
Charge1+2+3+Note 13-2-1-Note 2
Symbol of ionNa+Mg2+Al3+Note 1N3-O2-Cl-Note 2

Note 1: carbon and silicon in Group 4 usually form covalent bonds [covalent bond: A covalent bond between atoms forms when atoms share electrons to achieve a full outer shell of electrons. ] by sharing electrons.

Note 2: the elements in Group 0 do not react with other elements to form ions.

Back to Structure and bonding index

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