Write one main characteristic of d-block elements or transition elements

Explanation

### Step-by-Step Text Solution

1. **Identify the Group of Elements**: D-block elements are also known as transition elements. These elements are found in the central block of the periodic table, specifically groups 3 to 12.

2. **State the Main Characteristic**: One main characteristic of d-block or transition elements is that they have high melting and boiling points.

3. **Explain the Reason**: The high melting and boiling points of d-block elements are attributed to the involvement of a greater number of electrons in metallic bonding. Specifically, these elements utilize not only their outermost s electrons (ns) but also the (n-1)d electrons in bonding.

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