Question

What are the important oxidation states of lanthanide elements?

Hint:

Lanthanides commonly show +3 oxidation state; +2 and +4 states are also seen in a few cases due to f-orbital stability.

Answer 1

Step 1: General information.
Lanthanides are the 14 elements following lanthanum (Z = 57) from cerium (Ce) to lutetium (Lu). They belong to the f-block of the periodic table.
Step 2: Common oxidation state.
The most common oxidation state of lanthanides is +3, because after losing three electrons, they achieve a stable configuration with half-filled or fully filled f-subshells.
Step 3: Other oxidation states.
Some lanthanides also exhibit +2 and +4 oxidation states due to the stability of f$^0$, f$^7$, and f$^{14}$ configurations.
Examples:
- Ce → +4 (Ce$^{4+}$)
- Eu → +2 (Eu$^{2+}$)
- Yb → +2 (Yb$^{2+}$)
- Tb → +4 (Tb$^{4+}$)
Step 4: Explanation.
This variable oxidation state arises due to the small energy difference between 4f, 5d, and 6s orbitals.