Which of the following element about transition elements is incorrect ?

Options

A. They show variable oxidation states
B. All the ions are coloured
C. They exhibit diamagnetic and paramagnetic properties
D. They exhiibit catalytic property

Answer

To determine which statement about transition elements is incorrect, we need to analyze the provided statements one by one.

### Step-by-Step Solution:

1. **Understanding Transition Elements**: Transition elements are defined as the d-block elements that have partially filled d-orbitals. They typically exhibit variable oxidation states, are colored, and can act as catalysts.

2. **Analyzing the Statements**:
- **Statement 1**: "Variable oxidation states exist."
- This statement is correct. Transition metals can exhibit multiple oxidation states due to the involvement of d-electrons in bonding.

- **Statement 2**: "All transition metal ions are colored."
- This statement is incorrect. While many transition metal ions are colored due to d-d transitions (where an electron jumps between d-orbitals), not all transition metal ions are colored. For example, zinc (Zn²⁺) has a full d-subshell (d10) and does not exhibit d-d transitions, hence it is colorless.

- **Statement 3**: "They exhibit paramagnetic and diamagnetic properties."
- This statement is correct. Transition metals can be paramagnetic (due to unpaired electrons) or diamagnetic (if all electrons are paired).

- **Statement 4**: "They exhibit catalytic properties."
- This statement is also correct. Transition metals often act as catalysts in various chemical reactions.

3. **Conclusion**: Based on the analysis, the incorrect statement is that "all transition metal ions are colored."

### Final Answer:
The incorrect statement about transition elements is: "All transition metal ions are colored."