Transition metals are not characterized by:

Options

A. Fixed valency
B. coloured compound
C. high melting and boiling points
D. tendency to form coomplexes

Answer

To solve the question "Transition metals are not characterized by:", we will analyze the characteristics of transition metals and identify which of the given options does not apply to them.

### Step-by-Step Solution:

1. **Understanding Transition Metals:**
Transition metals are elements found in the d-block of the periodic table. They typically have partially filled d-orbitals. This unique electronic configuration gives them specific properties.

2. **Analyzing the Options:**
The options provided are:
- A) Fixed valency
- B) Scalar compounds
- C) High melting and boiling points
- D) Tendency to form complexes

3. **Evaluating Each Option:**
- **A) Fixed Valency:** Transition metals are known for having variable oxidation states (valencies). For example, iron can exhibit +2 and +3 oxidation states. Therefore, they do not have a fixed valency.
- **B) Scalar Compounds:** This term is not commonly associated with transition metals. Transition metals can form various types of compounds, but "scalar" is not a recognized characteristic.
- **C) High Melting and Boiling Points:** Transition metals generally have high melting and boiling points due to strong metallic bonding resulting from the presence of unpaired d-electrons.
- **D) Tendency to Form Complexes:** Transition metals readily form complexes with ligands due to their ability to accept electron pairs into their d-orbitals.

4. **Conclusion:**
Based on the analysis, the characteristic that transition metals are not characterized by is **A) Fixed Valency**. This is because they exhibit variable valency, which is a defining feature of transition metals.

### Final Answer:
Transition metals are not characterized by **fixed valency**.