Lanthanoids and actinoids are f-block elements in which the last electron enters the anti-penultimate energy level. The most common oxidation state of lanthanoids is +3, though +2 and +4 oxidation states are exhibited by some of the elements. In lanthanoid series, there is a progressive decrease in atomic and ionic radii, known as lanthanoid contraction. Unlike lanthanoids, actinoids show a large number of oxidation states.
Name two lanthanoids which exhibit +2 oxidation state.

Explanation

To answer the question regarding the lanthanoids that exhibit a +2 oxidation state, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding Lanthanoids**:
- Lanthanoids are a series of 15 elements from atomic number 57 (Lanthanum) to 71 (Lutetium). They are f-block elements where the last electron enters the 4f subshell.

2. **Common Oxidation States**:
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