The most common and stable oxidation state of a lanthanide is

Options

A. `+2`
B. `+3`
C. `+4`
D. `+1`

Answer

B

Explanation

In the lanthanoids, Ln `(+3)` compounds are prdominant species. However, occasionally `+2` and `+4` ions in solution or insolid compounds are also obtained. In forming tripositive lanthanide ions, the `ns^(2)` (n = 6) electrons are lost along with the `(n-1)d^(1)` electron. In the absence of `(n-1)d^(1)` electrons present in the (n-2)f subshell is lost. Further involvement of (n - 2)f electrons is ruled out because the 4f electrons in the antepenultimate shell are very effectively shielded from their chemical enviroment outside the atom by the 5s and 5p electrons. Consequently more 4f electrons do not take part in bonding i.e., they are neither removed to produce ions nor do they take any significant part in crystal field stabilization of complexes.