Properties Of Ionic Compounds - OCR 21C - BBC Bitesize - BBC

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1. Group 0 elements
2. Chemical properties of the noble gases
3. Forming ions
4. Forming negative ions
5. Forming ionic compounds
6. Limitations of models of ions and ionic compounds
7. Properties of ionic compounds

Properties of ionic compounds

The physical properties of ionic compounds can be explained by their giant ionic lattice structure and ionic bonds.

Learn more on the properties of ionic compounds in this podcast.

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Melting points

Ionic compounds are held together by many strong electrostatic forces between the oppositely charged ions. A lot of energy is needed to overcome these ionic bonds, so ionic compounds have high melting points.

Ionic compound	Melting point
NaCl	801°C
MgO	2,852°C

Ionic compound	NaCl
Melting point	801°C

Ionic compound	MgO
Melting point	2,852°C

Key factIonic compounds have high melting points and are therefore in the solid state at room temperature.

Conduction of electricity

A substance can conduct electricity if:

• it contains charged particles, and
• these particles are free to move from place to place

Ionic compounds conduct electricity when molten (liquid) or in aqueous solution (dissolved in water), because their ions are free to move from place to place. Ionic compounds cannot conduct electricity when solid, as their ions are held in fixed positions and cannot move.

Key factIonic compounds are conductors of electricity when molten or in solution, and insulators when solid.

Solubility

Not all ionic substances are soluble and some are more soluble than others.

When an ionic compound is added to water and dissolves it separates into its separate ions. The ions are surrounded by water molecules.

Although a water molecule is neutral overall, it has a weak positive charge near its hydrogen atoms, and a weak negative charge near its oxygen atom. Water molecules surround the ions in solution because they are attracted by the charges of the ions.

Next upListen to an audio clipPrevious pageLimitations of models of ions and ionic compounds

More guides on this topic

• How have our ideas about atoms changed over time? - OCR 21st Century
• What does the periodic table tell us about the elements?
• How are equations used to represent chemical reactions?

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