Choose the correct statement from the following :

1. Standard enthalpy of formation for alkali metal bromides becomes more negative on desending down the group. 

2. In case of CsI, lattice energy is less, but Cs+ is having less hydration enthalpy due to which it is less soluble in water.

3. For alkali metal fluorides, the solubility in water increases from lithium to caesium. LiF is least soluble in water.

4. Standard enthalpy of formation for LiF is most negative among alkali metal fluorides.