JEE Main Chemistry Class 11 Classification of Elements and Periodicity in Properties 1 Questions

Generally, the ionization enthalpies or energy increases from left to right in a period and decreases from top to bottom in a group. Several factor such as atomic radius, nuclear charge, shielding effect are responsible for change of ionization enthalpies. Here, Ist ionization enthalpy of A and B is greater than group I (Li 520kJmol−1 to Cs 374kJmol−1 ), which means element A and B belong to group −2 and all three given ionization enthalpy values are less for element B means B will come below A.