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Question
Ionisation enthalpies of Ce, Pr and Nd are higher than Th, Pa and U. Why?
Solution
When electrons start accommodating the 4f and 5f orbitals, the 5f electrons penetrate less into the inner core. They are more effectively shielded nuclei in comparison to 4f-electrons in lanthanides. This leads to the fact that 5f-electrons experience reduced nuclear force of attraction and hence they have Lower ionisation enthalpies than lanthanoids.
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| List - I | List - II | ||
| (a) | \[\ce{[Fe(CN)6]^3-}\] | (i) | 5.92 BM |
| (b) | \[\ce{[Fe(H2O)6]^3+}\] | (ii) | 0 BM |
| (c) | \[\ce{[Fe(CN)6]^4-}\] | (iii) | 4.90 BM |
| (d) | \[\ce{[Fe(H2O)6]^2+}\] | (iv) | 1.73 BM |
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