JEE Chemistry 2025 Question with Solution

Given: The successive ionisation energies are $800 \, \text{kJ/mol}$, $2427 \, \text{kJ/mol}$, $3658 \, \text{kJ/mol}$, $25024 \, \text{kJ/mol}$ and $32824 \, \text{kJ/mol}$.

Find: The group of the element.

Ionisation energy increases with the removal of each electron, but a very large increase indicates that the next electron is being removed from a stable inner shell.

Here, the major jump is between the $3^{\text{rd}}$ and $4^{\text{th}}$ ionisation energies:

$$3658 \, \text{kJ/mol} \rightarrow 25024 \, \text{kJ/mol}$$

This shows that after removal of $3$ electrons, the atom reaches a comparatively stable configuration, so the element has $4$ valence electrons.

Elements with $4$ valence electrons belong to Group $14$.

Therefore, the correct option is B.

Given: Successive ionisation energies are:

1. $800 \, \text{kJ/mol}$
2. $2427 \, \text{kJ/mol}$
3. $3658 \, \text{kJ/mol}$
4. $25024 \, \text{kJ/mol}$
5. $32824 \, \text{kJ/mol}$

Find: The group of the element.

Step 1: Understand the trend. Ionisation energy generally increases as electrons are removed because the remaining electrons are held more strongly by the nucleus.

Step 2: Identify the sharp rise. The largest increase occurs from the $3^{\text{rd}}$ to the $4^{\text{th}}$ ionisation energy:

$$25024 - 3658$$

This sharp rise means the $4^{\text{th}}$ electron is being removed from an inner stable shell.

Step 3: Infer valence electrons. If the big jump occurs after removal of $3$ electrons, then those removed electrons are outer electrons, and the element is inferred to have valence-shell behaviour corresponding to $4$ valence electrons.

Conclusion: The element belongs to Group $14$.

The correct option is B.