The incorrect statement regarding transition elements is

Options

A. They have low tensile strength
B. Their melting and boiling points are very high
C. They are good conductors of heat
D. Their density is very high.

Explanation

To determine the incorrect statement regarding transition elements, let's analyze each option step by step.

### Step 1: Understanding Transition Elements
Transition elements are metals found in the d-block of the periodic table. They include elements from Scandium (Sc) to Zinc (Zn) in the first series (3d), Yttrium (Y) to Cadmium (Cd) in the second series (4d), and Lanthanum (La) to Mercury (Hg) in the third series (5d). They are characterized by the presence of d-electrons.

**Hint:** Remember that transition elements are located in the d-block of the periodic table and have unique properties due to their d-electrons.

### Step 2: Analyzing Tensile Strength
The first statement claims that transition elements have low tensile strength. Tensile strength refers to the ability of a material to withstand tension without breaking. Transition metals typically exhibit high tensile strength due to strong metallic bonds formed by the delocalization of d-electrons.

**Hint:** Consider the nature of metallic bonding in transition metals and how it contributes to their strength.

### Step 3: Melting and Boiling Points
The second statement asserts that transition elements have high melting and boiling points. This is true because the presence of d-electrons contributes to strong metallic bonding, resulting in high melting and boiling points.

**Hint:** High melting and boiling points are often associated with strong bonding in metals.

### Step 4: Conductivity
The third statement states that transition elements are good conductors of heat. This is also correct. The structure of transition metals allows electrons to move freely, facilitating the conduction of heat and electricity.

**Hint:** Think about how the arrangement of atoms in metals allows for the movement of electrons.

### Step 5: Density
The fourth statement claims that transition elements have high density. This is true as well. Transition metals have relatively high atomic masses and smaller atomic radii, leading to higher density.

**Hint:** Density is influenced by both atomic mass and atomic size; heavier and smaller atoms generally result in higher density.

### Conclusion
After analyzing all the statements, the incorrect statement regarding transition elements is that they have low tensile strength. In reality, transition elements possess high tensile strength due to strong metallic bonding.

**Final Answer:** The incorrect statement is: "They have low tensile strength."