Select the incorrect statement about transition elements.

Options

A. The last electron enters in the d-orbital
B. Their properties are in between s and p-block elements
C. Scandium is the transition element with smallest atomic radii
D. Their common oxidation states are `+2`, `+3`

Answer

To solve the question of selecting the incorrect statement about transition elements, we will analyze each statement provided in the question step by step.

### Step-by-Step Solution:

1. **Understanding Transition Elements**:
- Transition elements are defined as elements that have partially filled d-orbitals. They typically belong to groups 3 to 12 of the periodic table.

2. **Evaluating Statement A**:
- **Statement A**: "The last electron enters in d-orbital."
- This statement is true. In transition metals, the last electron indeed enters the d-orbital. Therefore, this statement is correct.

3. **Evaluating Statement B**:
- **Statement B**: "Their properties are in between S and P block."
- This statement is also true. The properties of transition metals (d-block elements) are intermediate between the s-block and p-block elements. Hence, this statement is correct.

4. **Evaluating Statement C**:
- **Statement C**: "Scandium is the transitional element with the smallest atomic radii."
- This statement is incorrect. As we move across the period from scandium (Sc) to titanium (Ti), the atomic radii decrease. Titanium has a smaller atomic radius than scandium. Therefore, this statement is false.

5. **Evaluating Statement D**:
- **Statement D**: "Their common oxidation states are +2 and +3."
- This statement is true. Transition metals commonly exhibit oxidation states of +2 and +3 due to the loss of electrons from both the s and d orbitals. Thus, this statement is correct.

### Conclusion:
The incorrect statement about transition elements is **Statement C**: "Scandium is the transitional element with the smallest atomic radii."