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Ionic Compound

Key Stage 4

Meaning

An ionic compound is a molecule formed from 2 or more elements which have transferred electrons to become ions.

About Ionic Compounds

Ionic compounds form when atoms lose one or more electrons to become a positive ions and other atoms gain electrons to become negative ions. The electrostatic force of attraction between these ions is a strong chemical bond.
Metal elements form positive ions because it is easier for them lose electrons than gain electrons to get a full outer shell. Metals are on the left hand side of the Periodic Table and usually have either 1, 2, 3 or 4 electrons in the Outer Shell.
Group 1 Elements all form +1 ions; Li+1, Na+1, K+1
Group 2 Elements all form +2 ions; Be+2, Mg+2, Ca+2
Group 3 Elements all form +3 ions; Al+3
Transition Metal Elements can form different ions which are shown by Roman Numerals; Iron can form Fe(II) which is Fe+2 or Fe(III) is Fe+3,

Manganese can form Mn (II) which is Mn+2 or Mn (IV) which is Mn +4

Non-metal elements form negative ions because it is easier for them to gain electrons than lose electrons to get a full outer shell. Non-metals are on the right hand side of the Periodic Table and usually have 4, 5, 6, 7 or 8 electrons in their outer shell.
Group 5 Elements all form -3 ions; N-3, P-3
Group 6 Elements all form -2 ions; O-2, S-2
Group 7 Elements all form -1 ions; F-1, Cl-1
Some covalent compounds can form negative ions; Carbonate forms -2 ions CO3-2, Sulphate forms -2 ions SO4-2, Nitrate forms -1 ions NO3-1

Examples

LithiumIonFormation.png
MagnesiumIonFormation.png
AluminiumIonFormation.png
Lithium forms +1 ions. Magnesium forms +2 ions. Aluminium forms +3 ions.
ChlorineIonFormation.png
OxygenIonFormation.png
NitrogenIonFormation.png
Chlorine forms -1 ions. Oxygen forms -2 ions. Nitrogen forms -3 ions.

Bulk Properties

In their solid state ionic compounds are poor electrical conductors because the ions are not free to move.
In their liquid state ionic compounds are good electrical conductors because the electrically charged ions are free to move.
Most ionic compounds are soluble in water.
When dissolved in solution ionic compounds are good electrical conductors because the electrically charged ions are free to move.
Ionic compounds form giant ionic structures which have high melting points due to the strong electrostatic force between the ions.
State Electrical Conductivity Reason
Solid Poor Ions are in fixed positions and not free to move.
Liquid (Molten) Good Ions are free to move in the liquid.
Dissolved in Solution (Aqueous) Good Ions are free to move through solution.

References

Edexcel

Ionic compounds, page 180, GCSE Combined Science, Pearson Edexcel
Ionic compounds, page 36, GCSE Chemistry, Pearson, Edexcel
Ionic compounds, pages 20-22, GCSE Chemistry; The Revision Guide, CGP, Edexcel
Ionic compounds, pages 49-55, GCSE Chemistry, CGP, Edexcel
Ionic compounds, pages 83-85, GCSE Combined Science; The Revision Guide, CGP, Edexcel
Ionic compounds; properties, pages 38-39, GCSE Chemistry, Pearson, Edexcel

OCR

Ionic compounds, pages 19, 25, 35, Gateway GCSE Chemistry; The Revision Guide, CGP, OCR
Ionic compounds, pages 58-59, 77, 79, 88-89, 122, Gateway GCSE Chemistry, Oxford, OCR
Ionic compounds, pages 90, 91, 97, 108, Gateway GCSE Combined Science; The Revision Guide, CGP, OCR