The common oxidation state shown by actinoids is +3 with the other oxidation states being +4, +5, +6, and +7.

Question

The common oxidation state shown by actinoids is +3 with the other oxidation states being +4, +5, +6, and +7. Rank the following elements in decreasing order of the number of oxidation states they display:
A. Np ($Z=93$)
B. Am ($Z=95$)
C. Ac ($Z=89$)
D. Pa ($Z=91$)

Choose the correct answer from the options given below:

Accepted Answer

According to the known oxidation states of actinoids :
- Np (Neptunium, $Z=93$) exhibits 5 oxidation states: +3, +4, +5, +6, and +7.
- Am (Americium, $Z=95$) exhibits 4 oxidation states: +3, +4, +5, and +6.
- Pa (Protactinium, $Z=91$) exhibits 3 oxidation states: +3, +4, and +5.
- Ac (Actinium, $Z=89$) exhibits only 1 oxidation state: +3.
Therefore, the decreasing order of the number of oxidation states displayed is Np > Am > Pa > Ac, which corresponds to the sequence A > B > D > C.

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