Question

Which of the following oxidation states is common for all lanthanides?
A.) $+ 2$
B.) $+ 3$
C.) $+ 4$
D.) $+ 5$

Answer 1

The oxidation state of an element is the total number of electrons that an element has lost or gained. If the oxidation state of an element is positive then it means that element has lost the electrons and if the oxidation state of an element is negative then it means that element has gained the electrons.

Complete step by step answer:
The Lanthanides are a series of chemical elements from the atomic number $57$ to the atomic number $71$ from lanthanum element to the lutetium element. All fifteen lanthanides are metallic in nature. The lanthanides consist of elements present in the sixth period of the f-block in the periodic table. Lanthanides have $f -$subshell in their electronic configuration.
All elements of the lanthanides show variable oxidation states. These elements show $+ 2, + 3, + 4$ oxidation states. As we know that outer shells in electronic configuration of lanthanides are mostly $4f$ and $5d$. The number of oxidation states of the lanthanides are limited because of the large energy gap between $4f$ and $5d$ orbitals. The presence of $f -$subshell has a great influence on the oxidation states of the lanthanides. Among all the oxidation states, the most common oxidation state which is exhibited by every lanthanide is $+ 3$ oxidation state.

Hence, B.) option is the correct answer.

Note:
Remember that Lanthanides shows variable oxidation states like $+ 2, + 3, + 4$ but among all of them $+ 3$ is the most common oxidation state as the lanthanides lies in group three therefore these have plus three oxidation state as the most common oxidation state.