If first ionization enthalpies of elements X and Y are 419 kJ mol-1 and 590 kJ mol-1, respectively and second ionization enthalpies of X and Y are 3069 kJ mol-1 and 1145 kJ mol-1, respectively. Then correct statement is :
- Both X and Y are alkaline earth metals
- X is an alkali metal and Y is an alkaline earth metal
- X is an alkaline earth metal and Y is an alkali metal
- Both X and Y are alkali metals
Answer
(2) X is an alkali metal and Y is an alkaline earth metal
Solution
X: i H2 i H1 (3069 vs 419) after losing one electron X attains a noble gas configuration; the second electron comes from an inner shell X is an alkali metal (K).
Y: i H2 is only about twice i H1 (1145 vs 590) two valence electrons are removed easily Y is an alkaline earth metal (Ca).
Answer: (2)