QJEEM24Ch45c6: JEE Main 2024 Chemistry - Class 11 JEEM24Ch45c6 Solution: Given below are two statements : Statement I : The metallic…

To determine the correctness of the given statements, let's analyze each one individually based on atomic and ionic radii concepts.

Statement I:

The metallic radius of $\mathrm{Na}$ is $1.86\, \text{Å}$ and the ionic radius of $\mathrm{Na}^+$ is lesser than $1.86\, \text{Å}$ .

Analysis:

Metallic Radius of Sodium ( $\mathrm{Na}$ ):

Sodium is a metal, and its metallic radius is indeed approximately $1.86\, \text{Å}$ .

The metallic radius refers to half the distance between the nuclei of two adjacent atoms in a metallic lattice.

Ionic Radius of Sodium Ion ( $\mathrm{Na}^+$ ):

When sodium loses an electron to form $\mathrm{Na}^+$ , it loses its outermost electron shell (the 3s orbital).

This results in a significant decrease in size due to:

Decrease in Electron-Electron Repulsion: Fewer electrons mean less repulsion among them.

Unchanged Nuclear Charge: The number of protons remains the same, so the effective nuclear charge per electron increases, pulling the remaining electrons closer to the nucleus.

The ionic radius of $\mathrm{Na}^+$ is approximately $0.95\, \text{Å}$ , which is significantly smaller than $1.86\, \text{Å}$ .

Conclusion:

Statement I is correct.

Statement II:

Ions are always smaller in size than the corresponding elements.

Analysis:

General Trends:

Cations ( $\text{Positive Ions}$ ):

Formed by the loss of one or more electrons.

Result: Cations are smaller than their parent atoms due to loss of electron(s) and decreased electron-electron repulsion.

Example: $\mathrm{Na} \rightarrow \mathrm{Na}^+$ (size decreases).

Anions ( $\text{Negative Ions}$ ):

Formed by the gain of one or more electrons.

Result: Anions are larger than their parent atoms due to added electron(s) and increased electron-electron repulsion.

Example: $\mathrm{Cl} \rightarrow \mathrm{Cl}^-$ (size increases).

Exceptions to Statement II:

Since anions are larger than their corresponding neutral atoms, the statement that "ions are always smaller in size than the corresponding elements" is incorrect.

Conclusion:

Statement II is false.

Final Answer:

Statement I is correct but Statement II is false.