Question

Which of the following oxidation states is the most common among the lanthanoids?

• A. 4
• B. 2
• C. 5
• D. 3

Answer 1

The correct option is D 3

The Lanthanides have the general electron configuration of $\left[Xe\right]4f^{n}6s^2$ with the exception of La, Gd and Lu which have one 5d electron.

The common stable oxidation state of all the lanthanides is $+3$. It is attained by removing outermost 2 electrons of 6s electrons and 1 electron from 4f electrons. It is due to high energy difference in 4f and 6s, it is difficult to remove more electrons from 4f sub-shell.

The oxidation state of + 2 and + 4 are also exhibited by some of the elements. These oxidation states are only stable in those cases where stable $4f^0$, $4f^7$ or $4f^{14}$ configuration are achieved.

Hence, option $D$ is correct.