Why is first ionization energy of 5d elements higher than those of 3d and 4d elements ?

Explanation

To understand why the first ionization energy of 5d elements is higher than those of 3d and 4d elements, we can break down the explanation into several key points:

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
- Ionization energy is the energy required to remove an electron from an atom in its gaseous state. Higher ionization energy means that it is more difficult to remove an electron.

2. **Comparing 3d, 4d, and 5d Elements**:
...