MCQ
Thalium shows different oxidation states because
- AIt is a transition element
- ✓Of inert pair effect
- COf its amphoteric character
- DOf its higher reactivity
Electronic configuration of Thallium is $[ Xe ] \,4 f ^{14} \,5 d ^{10}\, 6 s ^2 \,6 p ^1$.
$d$ and $f$ electrons of inner shells provide poor shielding, thus the attraction of the nucleus on the $s$ electrons of the outermost shell increases. This is called the inert pair effect.
Whereas, $s$ electrons provide strong shielding to $p$ electrons, thus making it easy for the $p$ electrons to be released.
Thus, although Thallium shows $+3$ and $+1$ oxidation states, $+1$ is more common.
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($A$) $\mathrm{BrF}_5$ ($B$) $\mathrm{ClF}_3$ ($C$) $\mathrm{XeF}_4$ ($D$) $\mathrm{SF}_4$