Consider the following ionization enthalpies of two elements ' $A$ ' and ' $B$ ' : \ Which of the f

Question

Consider the following ionization enthalpies of two elements ' $A$ ' and ' $B$ ' : \ Which of the following statements is correct?\

Professor PC Thomas Classes · Answer

(b) : As the third ionisation energy of $A$ and $B$ are very high as compared to corresponding second ionisation energy, thus, there must be two electrons in their valence shells. Hence, elements $A$ and $B$ belong to group-2. On going down the group, the atomic size increases, so force of attraction between valence electron and nucleus decreases. Hence, ionization energy decreases. Thus, ' $B$ ' comes below ' $A$ '.\