Properties of ionic compounds
The physical propertiesA description of the appearance of a substance or how it acts without involving chemical reactions. For example, state, melting point, conductivity, etc. of ionic compoundAn ionic compound occurs when a negative ion (an atom that has gained an electron) joins with a positive ion (an atom that has lost an electron). can be explained by their giant ionic latticeThe structure of ionic compounds formed from millions of oppositely charged ions in a 3 dimensional arrangement. structure and ionic bondingIonic bonding forms between two atoms when an electron is transferred from one atom to the other, forming a positive-negative ion pair..
Learn more on the properties of ionic compounds in this podcast.
Listen to the full series on ±«Óătv Sounds.
Melting points
Ionic compounds are held together by many strong electrostatic forceA force of attraction between particles with opposite charges. forces between the oppositely charged ionElectrically charged particle, formed when an atom or molecule gains or loses electrons.. A lot of energy is needed to overcome these ionic bonds, so ionic compounds have high melting points.
| Ionic compound | Melting point |
| NaCl | 801°°ä |
| MgO | 2,852°°ä |
| Ionic compound | NaCl |
|---|---|
| Melting point | 801°°ä |
| Ionic compound | MgO |
|---|---|
| Melting point | 2,852°°ä |
Conduction of electricity
A substance can conduct electricity if:
- it contains charged particlesParticles, usually ions or electrons, that carry electrical charges., and
- these particles are free to move from place to place
Ionic compounds conduct electricity when moltenA term used to describe a liquid substance (eg rock, glass or metal) formed by heating a solid. (liquid) or in aqueousDissolved in water to form a solution. Shown as (aq) in chemical equations. 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.
Solubility
Not all ionic substances are solubleAble to dissolve in solvent. For example, sugar is soluble in water because it dissolves to form sugar solution. and some are more soluble than others.
When an ionic compound is added to water and dissolveWhen a substance breaks up and mixes completely with a solvent to produce a solution. it separates into its separate ions. The ions are surrounded by water moleculeA collection of two or more atoms held together by chemical bonds..
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.