Question

First ionization enthalpy of two elements X and Y are 500 KJ  mol^-1 and 375 KJ mol^-1 respectively. Comment about their relative position in a group as well as in a period. 

Answer 1

The ionization energy is the minimum energy required to remove the outermost electron from a gaseous neutral atom to form a cation.

Position in a group: X will be above Y ( because of ionization energy decreases down the group )

Position in a period: X will be the right side of Y ( because ionization energy increases from left to right)

Answer 2

Ionisation Enthalpy or potential is highest on the right side of the periodic table and lowest on the left side. Elements X and Y seem to be metals, which are on the left side of the table. Group I metals lose one electron each. Ionisation Enthalpy decreases in groups from top to bottom. In the IA group, X represents Sodium (Na) and Y represents Caesium (Cs). Also, X is in the third period and Y is in the sixth.