Which of the following elements exist in +5 oxidation state?
A. Actinium
B. Thorium
C. Protactinium
D. Uranium
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → C and D only
The actinoids show a wider range of oxidation states than the lanthanoids, because the 5f, 6d and 7s levels are of comparable energies. The states shown by the first members are:
A. Actinium — Incorrect. Ac shows +3 only.
B. Thorium — Incorrect. Th shows +3 and +4; its highest state is +4.
C. Protactinium — Correct. Pa shows +3, +4 and +5.
D. Uranium — Correct. U shows +3, +4, +5 and +6.