Although thallium (Z = 81) has only slightly higher atomic radius (170 pm)than that ofindium (167 pm)butits ionizationenthalpy (589 kJ "mol"^(-1))is much higherthan that ofindium (558 kJ "mol"^(-1)) . Explainwhy /

Although thallium (Z = 81) has only slightly higher atomic radius (170

1.	Although thallium (Z = 81) has only slightly higher atomic radius (170 pm)than that ofindium (167 pm)butits ionizationenthalpy (589 kJ "mol"^(-1))is much higherthan that ofindium (558 kJ "mol"^(-1)) . Explainwhy /
Answer» <html><body><p></p>Solution :Althrough on movingfrom `In (<a href="https://interviewquestions.tuteehub.com/tag/z-750254" style="font-weight:bold;" target="_blank" title="Click to know more about Z">Z</a> = 49)` to `<a href="https://interviewquestions.tuteehub.com/tag/tl-661220" style="font-weight:bold;" target="_blank" title="Click to know more about TL">TL</a> (Z = 81)`, the nuclearincreases by 32units `(81-49)`yet due to poor <a href="https://interviewquestions.tuteehub.com/tag/shielding-1205359" style="font-weight:bold;" target="_blank" title="Click to know more about SHIELDING">SHIELDING</a> effect on intervening 4f- and5d-electrons,effectivenuclear chargeaction on Tl is much higherthan that on Inand hence `Delta_(i)H_(1)`of `Tl`is much higherthan that of `In`.</body></html>