The Halogens

• group 7 - the reactivity increases as you go up the group as atomic radius decreases, less shielding, nuclear attraction increases (all outweigh the nuclear charge)
• boiling point increases as you go down the group as the London forces gets stronger

  F2 - yellow gas and yellow vapour (most toxic)

  Cl2 - green gas and green vapour

  Br2 - red-brown liquid and orange vapour and orange solution

  I2 - grey solid and purple vapour and brown solution
• displacement reaction - the most reactive elements displaces the less reactive element from its compound