Account for the following :
(b) The Ist ionization energy of the 5d series are higher than 3d and 4d, transition elements in respective groups.

Explanation

To account for the observation that the first ionization energy of the 5d series is higher than that of the 3d and 4d transition elements in their respective groups, we can break down the explanation into several key points:

### Step-by-Step Explanation:

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

**Hint**: Remember that ionization energy increases across a period and decreases down a group in the periodic table.
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