Metallic bonding – GCSE, Alevel for Edexcel and OCR

For OCR and Edexcel exam boards.
Metals have unique properties and can’t be classified as being ionic or covalent compounds.

Definition
“Metallic bonding is the electromagnetic interaction between delocalized electrons”

Common physical properties
• Shiny in appearance.
• Conduct electricity
• Conduct heat
• Ductile and malleable
• Hard and have high tensile strength

In metals the atoms lose their electrons in their incomplete outer shell. The atoms losing electrons become positive ions and the electrons now occupying a different energy level are delocalised. This bonding is often described as a ‘sea of electrons encircling the positive ion lattice.

The conduction of electricity is due to the delocalised electrons. The electrons are the charge carriers.
Heat conduction is especially effective through the vibration of the positive ions and the mobility of the electrons.

The diagram below shows metallic bonding.

Covalent bonding - GCSE and Alevel for OCR and Edexcel

Covalent Bonding
for OCR and Edexcel exam boards
Definition

“is a strong bond consisting of a shared pair of electrons”

Common properties include;

• Have low melting points (e.g. water) except for giant covalent structures

• Non-conductors

• May be insoluble in water

• Dissolve in organic solvents (e.g. ethanol)

A covalent bond forms between two non-metals when they share a pair of electrons. This happens because the negatively charged pair of electrons attract the positively charged nuclei. The electron pair will lie between the nuclei so that this attraction will exceed the repulsion of the positive nuclei. Now that the electrons are shared they are in molecular orbitals.

The diagram below is a dot-and cross-diagram of a water molecule

Ionic bonding - GCSE and Alevel for OCR and Edexcel

Ionic Bonding
For OCR and Edexcel exam boards

Definition:

"Ionic bonding is the electrostatic attraction between oppositely charged ions."

Common properties include:

· Are solids

· High melting points and boiling points

· Conduct electricity in aqueous solution an when molten

· Don’t conduct electricity when solid

These properties can be explained by the nature of the ionic bonds.

Ionics bonds are usually formed from a metal and a non-metal ion. Metallic elements usually form the positive ion when electrons are removed. The non-metallic atoms tend to gain electrons thus forming negative ion. So there is this transferral of electrons from metal to non-metal atoms. This will mean the atoms will have a complete outer shell of electrons and will have noble gas electronic configuration.

The presence of these ions causes the properties which are related to ionic bonds. These ions form a giant ionic lattice. The 3D arrangement depends on the ions relative size.

The diagram below shows a dot-and-cross diagram of Sodium Chloride (NaCl):