JEE Chemistry 2024 Question with Solution

Given: The task is to count how many of the listed ions have a noble gas configuration.

Find: The total number of such ions.

To determine whether an ion has a noble gas configuration, compare its electron configuration after ion formation with that of a noble gas.

From the extracted solution content:

• $\text{Sr}^{2+}$ gives $[\text{Kr}]$, so it has a noble gas configuration.
• $\text{Cs}^{+}$ gives $[\text{Xe}]$, so it has a noble gas configuration.
• $\text{La}^{3+}$ gives $[\text{Xe}]$, so it has a noble gas configuration.
• $\text{Yb}^{2+}$ gives $[\text{Xe}]$, so it has a noble gas configuration.
• $\text{Pb}^{2+}$ does not have a noble gas configuration.
• $\text{Fe}^{2+}$ does not have a noble gas configuration.

Therefore, the total number of ions with noble gas configuration is $4$.

The extracted the solution contains a contradiction because one place prints Correct Answer: $2$, while the actual working in the second approach identifies four ions. Using the solution working, the final answer is $4$.