Form 5 chemistry question

Free radicals:
very reactive, do not exist for long before they react with another molecule or atom.

Formation of free radicals:
generally an endothermic (requires energy input)

Free radical reaction:
It is an atom/group of atoms that contain a single, unshared, unpaired electron.

Example:
Halogen atom (Cl or Br).
Chlorine (Cl2) and Bromine (Br2) normally occur as diatomic molecules with a pair of electrons shared between the two atomes. When the bond between Chlorine atoms is broken (eg. by a photo of UV light), 2 chlorine atoms are produced. Each of these atoms contains 7 electrons in the valence shell (3 pairs & 1 unpaired electron). This makes a chlorine atom a free radical.

Things that trigger free radicals formation:
Light, UV, 300 degree C, peroxides are often used to initiate free radical formation.