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SQA National 5 Chemistry Bonding

Bonding

This page covers the following topics:

1. Ionic bonding
2. Covalent bonding
3. Metallic bonding

Ionic bonds form between cations (positive ions) and anions (negative ions). Many ionic compounds (salts) are formed by metals and non-metals. When an ionic bond is formed by a metal (usually from groups 1, 2) and a non-metal (usually from groups 6, 7), electrons are transferred from the metal atoms to the non-metal atoms to form metal cations and non-metal anions. The electrostatic attraction between these ions creates an ionic bond, which can be depicted using a dot-and-cross diagram.

Ionic bonding

Covalent bonds arise from the sharing of a pairs of electrons between two non-metal atoms. Covalent bonds are stronger than ionic or metallic bonds. Most molecules have covalent bonds. Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine exist naturally as diatomic molecules Hβ‚‚, Nβ‚‚, Oβ‚‚, Fβ‚‚, Clβ‚‚, Brβ‚‚, Iβ‚‚. For these diatomic molecules, the number of shared electron pairs in a molecule is the same as the number of unpaired electrons in a single atom. A single bond is formed when 2, a double when 4 and a triple when 6 electrons are shared.

Covalent bonding

Metallic bonding arises from the electrostatic attraction between positive metal cations and negative delocalised electrons. Delocalised electrons aren't associated with any particular metal atom, they move freely around the whole giant metallic structure. Since these delocalised electrons are free to move across a material, metals are good conductors of electricity. Metallic bonding can be present between atoms of a single metal or a mixture of different metals called alloys.

Metallic bonding

1

Draw a dot-and-cross diagram to represent an ionic bond in KBr.

Draw a dot-and-cross diagram to represent an ionic bond in KBr.

2

Which two groups of the periodic table are most cations in ionic compounds from?

Which two groups of the periodic table are most cations in ionic compounds from?

3

Which of the following compounds have metallic bonding within their structures?

β‹… water
β‹… barium
β‹… sodium chloride
β‹… methane
β‹… nickel
β‹… silicon

Which of the following compounds have metallic bonding within their structures? 

β‹… water 
β‹… barium 
β‹… sodium chloride 
β‹… methane 
β‹… nickel 
β‹… silicon

4

Why are metals good conductors of electricity?

Why are metals good conductors of electricity?

5

Draw a diagram depicting metallic bonding between 6 atoms of lithium.

Draw a diagram depicting metallic bonding between 6 atoms of lithium.

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