please explain the trends in hydration enthalpy and lattice enthalpy down the group of both alkali metals and alkaline earth metals.
Trends in Alkali metals
Hydration enthalpy of alkali metals:
The extent of hydration depends upon the size of the ions.
Smaller the size of the ion, greater is the hydration enthalpy.
Li+ > Na+ > K+> Rb+ > Cs+
Lattice energy of alkali metals:
The lattice energy decreases with the increase in the size of the cation i.e. from Li+ to Cs+
Trends in Alkaline earth metals
Hydration enthalpy of alkaline earth metals:
The hydration enthalpy becomes smaller as the size of the ion increases.
Be+2 > Mg+2 > Ca+2 > Sr+2 > Ba+2
Lattice energy of alkaline earth metals:
Lattice energy is directly proportional to charge and inversely proportional to the size.
On moving down the group, the metal ions increase in size and the lattice enthalpy decrease.