a) Magnesium + Chlorine -> Magnesium chloride ( Mg + Cl2 -> MgCl2)
b) Potassium + Oxygen -> Potassium oxide 
( 2K + O2 -> K2O ) 
c) Sodium + Bromine -> Sodium bromide 
( 2Na + Br2 -> 2NaBr) 
d) Carbon + Oxygen -> Carbon dioxide 
( C + O2 -> CO2 ) This reaction occurs when heated.