Formation of Covalent Bonds

Specification Point 1.28:
  • Explain how a covalent bond is formed when a pair of electrons is shared between two atoms.
  • Covalent bonds are formed when electrons are shared between atoms.
  • Only non-metal elements participate in covalent bonding.
  • As in ionic bonding, each atom gains a full outer shell of electrons.
  • Covalent bonds between atoms are strong and the bonded unit of atoms is what is called a molecule.
  • The forces that act between the molecules are weak intermolecular forces and are not chemical bonds.
HCl Sharing Electrons, Edexcel GCSE Chemistry

Diagram showing covalent bonding in HCl, where each atom donates 1 electron to the bonding pair of electrons


Specification Point 1.29:
  • Recall that covalent bonding results in the formation of molecules.
  • Covalently bonded substances tend to be small molecular structures such as H2O or CO2.
  • These small molecules are known as simple molecules and differ from ionic compounds which form larger lattice structures.
  • Other covalent molecules can be very large, such as polymers or giant covalent structures.

Size of Atoms & Molecules

Specification Point 1.30:
  • Recall the typical size (order of magnitude) of atoms and small molecules.
  • Simple molecular substances consist of molecules which contain atoms that are bound tightly together by strong covalent bonds.
  • These molecules are very small but the atoms themselves are smaller than the molecules.
  • Even though individual atoms and molecules are extremely small, developments in electron microscopy can produce images of atoms and simple molecules.

Pentacene (C22H14) was first imaged in 2009 by the IBM Research team in Zurich using a technique called atomic force microscopy

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.