Basic Biochemistry

Atoms and Ions

  • All matter is composed of atoms

  • Atoms are made up of protons, neutrons and electrons

  • Atoms are most stable when their electron shells are complete A

  • toms can lose or gain electrons to achieve this state – they become charged ions

  • The chemical properties of an element are determined by the number of electrons in the atom

  • Atoms gaining electrons are reduced to negative ions

  • Atoms losing electrons are oxidised to positive ions


  • Covalent bonds

    • electrons are shared between two atoms completing both outer shells

    • a molecule is formed - eg CO2



  • Ionic bonds

    • electrons are given from one atom to another

    • the resulting + and – charges form an electrostatic bond Eg NaCl

  • Hydrogen bonds

    • electrons are not evenly shared

    • one atom becomes slightly –ve and the other slightly +ve forming a weak electrostatic bond.

    • Many of these can have a significant bonding effect. Eg between water molecules