Halogens + CARBONATE TESTWatch
or is it co32- + HNO3 = NO3 + H20 + CO2
I'm with OCR A Chemistry btw...
Reactivity decreases as you go down group 7 because one shell is added as you descend. This means there will be more shielding between the inner electrons and also the atomic radius increases as you go down group 7 so the nuclear attraction would decrease. This means that the ionisation energy decreases so the ability to form 1- ions decreases as you go down the group.
How to understand this : If an incoming atom that wants to react with a halogen tries to react with a halogen with more shells (thus with a lower nuclear attraction) then obviously it'll repel the halogen more because the nuclear attraction is weaker down the group. Remember that bonding exists between the nucleus of an atom so less nuclear attraction = less bonding (or more scientifically, less reactivity).