Covalent Bonds | A Level Chemistry | OCR, AQA, Edexcel

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This week we are revising Covalent Bonds

A-Level Chemistry can be tough but fortunately we’ve made this tutorial to help you score the A* you need for questions on everything to do with Covalent Bonds.

A covalent bond is the bond formed between atoms that share electrons. Atoms share electrons to gain a full outer shell of electrons. Remember that they want to gain a full outer shell as this is when the atom is most stable and inert.

A single covalent bond contains a shared pair of electrons. Each covalent bond involves two electrons which makes up the shared pair of electrons. Each electron from the electron pair comes from each of the atoms involved in the covalent bond.

A molecule is made up of two or more atoms. When two or more atoms join together a molecule is made. E.g. two oxygen atoms form the O2 (oxygen) molecule. Four hydrogen atoms and a carbon atom make the CH4 (methane) molecule.

A covalent bond forms between atoms that are non-metals. The main form of bonding between non-metals is covalent bonds where non-metals share electrons in a bond.

The electrostatic attraction between the nuclei and the shared electrons maintain the covalent bond. The nucleus has an overall positive charge because it contains protons which have a positive charge and neutrons which have a neutral charge. This means that there is an electrostatic attraction between the positively charged nuclei and the negatively charged electrons. The electrostatic attraction holds the two atoms in the covalent bond together.

This figure shows what a covalent bond looks like between a carbon atom and a hydrogen atom in methane as well as a hydrogen and fluorine atom in hydrogen fluoride. There are two electrons in each covalent bond where each is represented by either a dot or a cross. Atomic orbitals of each atom involved in the covalent bond overlap so that each of them contributes one electron each to the covalent bond.

Atoms can form multiple covalent bonds as well has single covalent bonds. A multiple covalent bond can be either a double or triple covalent bond and it is when atoms share several pairs of electrons rather than just a single pair.

A double covalent bond is when atoms share two pairs of electrons. E.g. the covalent bond between two oxygen atoms involves sharing two pairs of electrons to gain a full outer shell.

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