Which of the following exhibits only +3 oxidation state?

Which of the following exhibits only +3 oxidation state?
  1. $U$
  2. $\mathrm{Th}$
  3. Ac
  4. $\mathrm{Pa}$

Solution

${ }_{89} \mathrm{Ac}=[\mathrm{Rn}] 6 d^1, 7 s^2$ Oxidation state $=+3$ ${ }_{90} \mathrm{Th}=[\mathrm{Rn}] 6 d^2, 7 s^2$ Oxidation states $=+3,+4$ ${ }_{91} \mathrm{~Pa}=[\mathrm{Rn}] 6 d^3, 7 s^2$ Oxidation states $=+3,+4,+5$ ${ }_{92} \mathrm{U}=[\mathrm{Rn}] 6 d^4, 7 s^2$ Oxidation states $=+3,+4,+5,+6$

Asked in: NEET 2012 (Mains)

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