Characteristics of Halogens
- Oxidation States
The electronic configuration of halogens is ns2, np5.
They require one electron to complete their octet. Thus, they all show -1 oxidation state. They also
show +1 oxidation state, if the combining element is more
electronegative than the halogen. Fluorine has the smallest atomic size,
is highly electronegative and does not have any vacant d-orbitals.
Hence, it does not show positive oxidation states. The other halogen
atoms show varied oxidation states, -1, +1, +3, +5 and +7. This is because they have
vacant d-orbitals in their valence shells. The s- and p-electrons
present in the outer shells can be easily promoted to these vacant
Halogens appear coloured as they absorb visible light, which causes
excitation of the outer electrons to higher energy levels. Fluorine has
a small atomic size, and therefore, absorbs violet light of higher
energy. It, therefore, appears pale yellow. Iodine absorbs yellow light
of lesser energy, and therefore, appears violet in colour. It is
observed that the colour of halogens deepens down the group.