Which statements are incorrect about transition elements ?

Options

A. They show variable valency
B. They readily form complex compounds
C. All their ions are colourless
D. Their ions contain partially filled d - orbital

Answer

To determine which statements about transition elements are incorrect, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: They show variable valency.**
- Transition elements are known for their ability to exhibit variable oxidation states due to the involvement of d-orbitals in bonding. For example, iron can exist in +2 and +3 oxidation states, and manganese can show oxidation states from +1 to +7. Therefore, this statement is **correct**.

2. **Statement 2: They readily form complex compounds.**
- Transition metals have vacant d-orbitals that allow them to accept electron pairs from ligands, which leads to the formation of complex compounds. For instance, iron(II) can form complexes with water or other ligands. This statement is also **correct**.

3. **Statement 3: All their ions are colorless.**
- This statement is **incorrect**. Transition metal ions typically exhibit color due to d-d transitions, where electrons move between d-orbitals in the presence of light. For example, the Cr³⁺ ion in solution is colored due to these transitions. While some ions may be colorless (like Zn²⁺), it is not true that all transition metal ions are colorless.

4. **Statement 4: Their ions contain partially filled orbitals.**
- Many transition metal ions have partially filled d-orbitals, which is a characteristic feature of these elements. For example, iron in the +2 oxidation state has the electron configuration of [Ar] 3d⁶, which is partially filled. Therefore, this statement is **correct**.

### Conclusion:
The **incorrect statement** about transition elements is **Statement 3: All their ions are colorless**.

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