The five successive ionisation energies energies of an element `'X'` are `800, 1427, 2658, 25024` and `32824 "KJ mole"^(-1)` respectively . The valency of `'X'` is `:`

Options

A. 3
B. 4
C. 2
D. 1

Explanation

To determine the valency of element 'X' based on the given successive ionization energies, we can follow these steps:

### Step-by-Step Solution:

1. **List the Ionization Energies**:
The given ionization energies are:
- IE1 = 800 kJ/mol
- IE2 = 1427 kJ/mol
- IE3 = 2658 kJ/mol
- IE4 = 25024 kJ/mol
- IE5 = 32824 kJ/mol

2. **Analyze the Changes in Ionization Energies**:
Observe the differences between successive ionization energies:
- Difference between IE1 and IE2: 1427 - 800 = 627 kJ/mol
- Difference between IE2 and IE3: 2658 - 1427 = 1231 kJ/mol
- Difference between IE3 and IE4: 25024 - 2658 = 22366 kJ/mol
- Difference between IE4 and IE5: 32824 - 25024 = 7800 kJ/mol

3. **Identify the Significant Jump**:
Notice that there is a significant jump in ionization energy between IE3 (2658 kJ/mol) and IE4 (25024 kJ/mol). This large increase indicates that after removing the third electron, the atom reaches a more stable electron configuration, likely resembling that of a noble gas.

4. **Determine the Number of Valence Electrons**:
Since the first three ionization energies are relatively low compared to the fourth, we can conclude that the element 'X' has 3 valence electrons. The removal of these three electrons leads to a stable electron configuration.

5. **Conclude the Valency**:
The valency of an element is defined as the number of electrons that an atom can lose, gain, or share to achieve a stable electron configuration. Since 'X' can lose 3 electrons to achieve stability, the valency of 'X' is 3.

### Final Answer:
The valency of element 'X' is **3**.

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