A-level Chemistry/OCR/Group 7

Group 7 consists of highly reactive non-metals called halogens.

Some main properties of the first 4 elements in group 7 are listed below.

halogen formula colour physical state electronic structure
fluorine F2 pale yellow gas 1s22s22p5
chlorine Cl2 greenish-yellow gas 1s22s22p63s23p5
bromine Br2 red-brown liquid 1s22s22p63s23p64s23d104p5
iodine I2 grey black, purple if in vapour form solid 1s22s22p63s23p64s23d104p65s24d105p5

The boiling and melting points increase as you go down the group. This is because the strength of the Van Der Waals forces (or induced dipole-dipole interactions) increases since the atoms have more electrons as you descend the group. This trend is highlighted by the fact that the physical state of the halogens changes from gaseous (fluorine) to solid (iodine) down the group. Volatility decreases down the group as the boiling points increase.

As you go down group 7, the halogens become less reactive.

This is because:

Decreasing reactivity,

- Atomic radius increases.

- Nuclear charge increases, so the nuclear attraction on the outer electrons are stronger.

- Electron Shielding increases and outweighs the nuclear attraction.



-Halogens are oxidising agents

-Halogen + electron -> Halide Ion or Reduction agent