JEE Chemistry 2025 Question with Solution

Given:

• Statement (I): The first ionization energy of $\text{Pb}$ is greater than that of $\text{Sn}$.
• Statement (II): The first ionization energy of $\text{Ge}$ is greater than that of $\text{Si}$.

Find: Which statement combination is correct.

Ionisation energy generally decreases down a group due to increasing atomic size and distance of electrons from the nucleus.

• Statement (I) is false: The ionisation energy of $\text{Pb}$ is lower than that of $\text{Sn}$ because $\text{Pb}$ is lower in the periodic table and has a higher atomic size.
• Statement (II) is true: $\text{Ge}$ has a higher ionisation energy than $\text{Si}$ because it is in the same group but higher in the periodic table, so its electrons are closer to the nucleus.

Therefore, the correct option is C.

Given:

• Compare the first ionization energies of $\text{Pb}$ and $\text{Sn}$.
• Compare the first ionization energies of $\text{Ge}$ and $\text{Si}$.

Find: Determine the truth values of Statement (I) and Statement (II).

Step 1: Analyze Statement (I). Statement (I) states that the first ionization energy of $\text{Pb}$ (Lead) is greater than that of $\text{Sn}$ (Tin). However, this is incorrect. Although $\text{Pb}$ and $\text{Sn}$ are in the same group (Group 14), lead ($\text{Pb}$) is lower in the periodic table compared to tin ($\text{Sn}$). As we move down a group, the atomic radius increases, and the outermost electrons are farther from the nucleus, leading to a lower ionization energy. Therefore, the first ionization energy of $\text{Pb}$ is less than that of $\text{Sn}$, making Statement (I) false.

Step 2: Analyze Statement (II). Statement (II) states that the first ionization energy of $\text{Ge}$ (Germanium) is greater than that of $\text{Si}$ (Silicon). This is true. $\text{Ge}$ is in Period 4 and $\text{Si}$ is in Period 3, so $\text{Si}$ has a smaller atomic radius and the outermost electrons are held more tightly by the nucleus, leading to a higher ionization energy. Therefore, the first ionization energy of $\text{Ge}$ is greater than that of $\text{Si}$, making Statement (II) true.

Step 3: Conclusion. Statement (I) is false, and Statement (II) is true.

$\boxed{\text{Statement I is false but Statement II is true.}}$

Therefore, the correct option is C.