Given below are two statements:

Statement I: In group 13, the stability of +1 oxidation state increases down the group.

Statement II : The atomic size of gallium is greater than that of aluminium.

In the light of the above statements, choose the most appropriate answer from the options given below :

<h3><strong>Statement I:</strong></h3> <p><strong>"In group 13, the stability of +1 oxidation state increases down the group."</strong></p> <p><strong>Analysis:</strong></p> <p><p><strong>Group 13 Elements:</strong></p></p> <p><p><strong>Boron (B)</strong></p></p> <p><p><strong>Aluminum (Al)</strong></p></p> <p><p><strong>Gallium (Ga)</strong></p></p> <p><p><strong>Indium (In)</strong></p></p> <p><p><strong>Thallium (Tl)</strong></p></p> <p><p><strong>Common Oxidation States:</strong></p></p> <p><p>The typical oxidation state for group 13 elements is <strong>+3</strong>.</p></p> <p><p>However, due to the <strong>inert pair effect</strong>, the <strong>+1 oxidation state becomes more stable</strong> as we move down the group.</p></p> <p><p><strong>Inert Pair Effect:</strong></p></p> <p><p>The reluctance of the s-electrons (ns²) in the valence shell to participate in bonding.</p></p> <p><p>This effect becomes more significant in heavier elements due to poor shielding by inner d and f orbitals.</p></p> <p><p><strong>Stability Trend:</strong></p></p> <p><p><strong>Boron (B):</strong> Exhibits only the +3 oxidation state.</p></p> <p><p><strong>Aluminum (Al):</strong> Predominantly +3 oxidation state.</p></p> <p><p><strong>Gallium (Ga):</strong> +3 is more stable, but +1 oxidation state starts appearing.</p></p> <p><p><strong>Indium (In):</strong> +1 oxidation state becomes significant.</p></p> <p><p><strong>Thallium (Tl):</strong> The +1 oxidation state is <strong>more stable</strong> than the +3 oxidation state.</p></p> <p><strong>Conclusion for Statement I:</strong></p> <p><p><strong>Correct.</strong></p></p> <p><p>The stability of the <strong>+1 oxidation state increases</strong> as we move down group 13 due to the inert pair effect.</p></p> <hr /> <h3><strong>Statement II:</strong></h3> <p><strong>"The atomic size of gallium is greater than that of aluminium."</strong></p> <p><strong>Analysis:</strong></p> <p><p><strong>Expected Trend:</strong></p></p> <p><p>Generally, atomic size <strong>increases</strong> down a group because each successive element has an additional electron shell.</p></p> <p><p><strong>Actual Atomic Radii:</strong></p></p> <p><p><strong>Aluminum (Al):</strong> Approximately <strong>143 picometers (pm)</strong></p></p> <p><p><strong>Gallium (Ga):</strong> Approximately <strong>135 pm</strong></p></p> <p><p><strong>Anomalous Behavior:</strong></p></p> <p><p>**Gallium's atomic radius is *<em>slightly smaller</em>* than that of aluminum.**</p></p> <p><p>This anomaly is due to the presence of <strong>10 d-electrons</strong> in gallium's electron configuration (Ga: [Ar] 3d¹⁰ 4s² 4p¹).</p></p> <p><p><strong>Poor Shielding Effect:</strong></p> <p><p><strong>3d electrons</strong> do not shield the nuclear charge effectively.</p></p> <p><p>As a result, the <strong>effective nuclear charge increases</strong>, pulling the outer electrons closer to the nucleus.</p></p></p> <p><p>This causes gallium to have a <strong>smaller atomic radius</strong> compared to aluminum.</p></p> <p><strong>Conclusion for Statement II:</strong></p> <p><p><strong>Incorrect.</strong></p></p> <p><p>The atomic size of gallium is <strong>less than</strong> that of aluminum due to poor shielding by d-electrons.</p></p> <hr /> <h3><strong>Final Answer:</strong></h3> <p><p><strong>Statement I is correct</strong>, as the stability of the +1 oxidation state increases down group 13.</p></p> <p><p><strong>Statement II is incorrect</strong>, because gallium has a smaller atomic radius than aluminum.</p></p> <hr /> <p><strong>Answer: Option B</strong></p>