The highest jump ion successive ionisation energy indicates a stable noble gas configuration. 
The highest jump is observed in the IE1&IE2. It shows the attainment of stable noble gas configuration of X after losing one electron. Hence, X is an alkali metal. The IE1 of Y is +590 kJ mol−1 which is greater than IE1 of X due to ns2 configuration. ∴X= Alkali metal and Y= Alkaline Earth metal