Correct Answer - C
In the free state, group 2 elements exhibit zero oxidation number. In the combined state, they exhibit only one valency (they are always bivalent) and only one oxidation number +2.
In spite of the fact that less energy is required to form `M^(+)` ions, group 2 elements prefer to from `M^(2+)` ions because in the solid state, the greater lattice enthalpy of `M^(2+)` ions because in the solid state, the greater lattice enthalpy of `M^(2+)` ions more than compensates for the higher 2nd ionization enthalpy. Similarly, in aqueous solution, it is the greater hydration enthalpy which more than compensates for the higher 2nd ionization enthalpy.
