What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group?
Within the main group elements,the ionization enthalpy decreases regularly as we move down the group. This is due to the following factors:
$(i)$ Atomic size: On moving down the group,there is a gradual increase in atomic size due to an additional main energy shell $(n)$.
$(ii)$ Shielding effect: There is an increase in shielding effect on the outermost electron due to an increase in the number of inner electrons.
$(iii)$ Nuclear charge: In going from top to bottom in a group,the nuclear charge increases.
The effect of the increase in atomic size and the shielding effect is much more than the effect of the increase in nuclear charge.
As a result,the electron becomes less tightly held to the nucleus as we move down the group.
Hence,there is a gradual decrease in the ionization enthalpies in a group.
$(i)$ Atomic size: On moving down the group,there is a gradual increase in atomic size due to an additional main energy shell $(n)$.
$(ii)$ Shielding effect: There is an increase in shielding effect on the outermost electron due to an increase in the number of inner electrons.
$(iii)$ Nuclear charge: In going from top to bottom in a group,the nuclear charge increases.
The effect of the increase in atomic size and the shielding effect is much more than the effect of the increase in nuclear charge.
As a result,the electron becomes less tightly held to the nucleus as we move down the group.
Hence,there is a gradual decrease in the ionization enthalpies in a group.
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| $A_{(g)} \to A^{+}_{(g)} + e^-, \ A_1$ | $B_{(g)} \to B^{+}_{(g)} + e^-, \ B_1$ |
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If the monovalent positive ion of $A$,divalent positive ion of $B$,and trivalent positive ion of $C$ have zero electrons,then which of the following is the incorrect order of the corresponding $I.E.$?
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