Group Seven :D

Trends:

1. Electronegativity. This increases as you go up the group.
   
2. Atomic Radius, increases as you go down the group.
   
3. Melting point, increases as you go down the group.
4. Boiling point, increases as you go down the group.
   
5. The oxidisng agent ability increases and you go up the group (so, Astetine to Fluorine.)

Their colours, in solution... Fluorine is clear, Cl is yellowy, Br is red/brown, and Iodene is purple.

The Sodium Hallides + Sulphuric Acid:

Eqn1 ...
NaCl (solid) + H2SO4 (liquid) => NaHSO4 (solid) + HCl (gas)
This produces steamy fumes of HCl

Eqn2 ...
- NaBr(s) + H2SO4(l) => NaSO4(s) + HBr(g) [Steamy fumes]
-- 2H+ + 2Br- + H2SO4 => SO2 (g) +2H2O(l) + Br(l) [Brown fumes]


Eqn3 ...
- NaI(s) + H2SO4(l) => NaH2SO4(s) + HI(g) [Steamy fumesof HI]
-- 2H+ + 2I- + H2SO4(aq) => H2S(g) + 4H2O(l) + I2(s) [Black solid forms, (I2), bad egg smell.]