Ionic bonding

Ionic bonding

• Ionic bonding occurs between positive and negative ions, which attract each other and bind together to form ionic compounds. For example, sodium chloride consists of Na+ ions and Cl- ions bound together.
• Positive and negative ions attract one another and bind together forming a new substance. This is called ionic bonding.
• For example:
• Sodium chloride consists of Na+ ions and Cl- ions bound together.
• Magnesium oxide consists of Mg2+ ions and O2- ions bound together.
• Ionic compounds like magnesium oxide and sodium chloride have high melting points and do not conduct electricity when solid. They do conduct electricity when molten. Sodium chloride is soluble in water and the solution conducts electricity.
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Metal Ions & Non Metal Ions

• In some circumstances metal atoms may lose electrons. The atom then has more protons than electrons and so it will be positively charged, a positive ion.
• Example: A magnesium atom may lose two electrons and become a Mg2+ ion.
• Non-metal atoms may gain electrons and become negatively charged.
• Example: An oxygen atom may gain two electrons and become an O2- ion

Ionic Lattice

• Each ion is surrounded by oppositely charged ions held in place by electrostatic attractionand forming an ionic crystal lattice.
• The number of ions in an ionic compound is such that the overall charge of a sample of the compound is zero.
• Example
• Magnesium chloride consists of Mg2+ and Cl -ions. Twice as many chloride ions as magnesium ions are needed to make the substance neutral. The formula of magnesium chloride is MgCl2.
• The ions in a crystal lattice are very strongly bonded together so a high temperature is required to separate the particles and melt the crystal. The ions are held strongly in position so they cannot move and carry an electric current.
• If an ionic compound is melted or dissolved in water the ions are then free to move and so the substance can be electrolysed.
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