chemistry-class-12-unit-07-chapter-01-some-p-block-elements-l-5-8-1wlbipddqua

<h4 id="successchemical-reactivity-of-group-2-elementssuccess"><Success>Chemical reactivity of group 2 elements</Success></h4>
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<ul>
<li>$\mathrm{Be}^{2+}>\mathrm{Mg}^{2+}>\mathrm{Ca}^{2+}>\mathrm{Sr}^{2+}>\mathrm{Ba}^{2+}$</li>
<li>Hydration enthalpy trend</li>
<li>$\mathrm{MgCl}_2, 6 \mathrm{H}_2 \mathrm{O},$</li>
<li>$\mathrm{CaCl}_2, 6 \mathrm{H}_2 \mathrm{O}$</li>
<li>$n s^2 \rightarrow n s^{\prime} n p^{\prime}$</li>
</ul>
<table>
<thead>
<tr>
<th>Metal</th>
<th>Be</th>
<th>Mg</th>
<th>Ca</th>
<th>Sr</th>
<th>Ba</th>
</tr>
</thead>
<tbody>
<tr>
<td>Colour</td>
<td>No</td>
<td>No</td>
<td>brick red</td>
<td>Crimson</td>
<td>Apple</td>
</tr>
<tr>
<td>$ \lambda $ in nm</td>
<td></td>
<td></td>
<td>662</td>
<td>650</td>
<td>554.5</td>
</tr>
</tbody>
</table>
<ul>
<li>
<p>Reactivity</p>
</li>
<li>
<p>Air (Oxygen); Water; $H_2$; $N_2$; halogens</p>
</li>
<li>
<p>Reducing nature; behavior in liquid $NH_3$</p>
</li>
</ul>
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<h4 id="successchemical-reactivity-of-group-2-elementssuccess-1"><Success>Chemical reactivity of group 2 elements</Success></h4>
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<ul>
<li>Smaller size compared to alkali metals; strongly hydrated; high lattice energy</li>
<li>Be has different chemistry compared to $\mathrm{Mg}, \mathrm{Ca}, \mathrm{Sr}, \mathrm{Ba}$ and $\mathrm{Ra}$</li>
<li>Free $\mathrm{Be}^{2+}$ does not exist; all its compounds are covalent or contain solvated ions such as $[{Be}(H_2O)_4]^{2+}$</li>
<li>Many of the salts are less soluble in water</li>
<li>$\mathrm{K}_2 \mathrm{SO}_4$ is soluble not $\mathrm{CaSO}_4$ and $\mathrm{SrSO}_4$</li>
<li>$\mathrm{Be}$ is a rare element</li>
<li>$Be_3Al_2Si_6O_{18}$ (Beryl)</li>
</ul>
</div>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/chemistry-class-12-unit-07-chapter-01-some-p-block-elements-l-5_8-1wlbipddqua-025-0460.8.jpg"></p>
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### <Success>Reaction</Success>
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<p>$[Be(H_2O)_4]^{2+} \quad [Al(H_2O)_6]^{3+}$</p>
<p>$[Be(H_2O)_4]^{2+} +H_2O \rightleftharpoons [(BeOH)(H_2O)_3]^+ +H_3O^+$</p>
<p>$[Be(OH)_3]_3^{3-} \quad Be(OH)_2 \quad BeO$ and $Be(OH)_2$</p>

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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/chemistry-class-12-unit-07-chapter-01-some-p-block-elements-l-5_8-1wlbipddqua-43.jpg"></p>
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#### <Success>Chemical reactivity of group 2 elements</Success>
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<p>$\mathrm{Ca}(\mathrm{OH})_2+\mathrm{H}_2 \mathrm{O}_2+6 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{CaO}_2 \cdot 8 \mathrm{H}_2 \mathrm{O} $</p>
<p>$  \mathrm{CaO}+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Ca}(\mathrm{OH})_2 ; \mathrm{Mg}^{2+}+2 \mathrm{OH} \rightarrow \mathrm{Mg}(\mathrm{OH})_2$</p>
<p>$Ba(OH)_2$ is the most stable and most soluble hydroxide</p>
<table>
<thead>
<tr>
<th>Oxide</th>
<th>Lattice E (kJ/mol)</th>
<th>M.P. (°C)</th>
</tr>
</thead>
<tbody>
<tr>
<td>BeO</td>
<td>-4298</td>
<td>2507</td>
</tr>
<tr>
<td>MgO</td>
<td>-3800</td>
<td>2800</td>
</tr>
<tr>
<td>CaO</td>
<td>-3419</td>
<td>1728</td>
</tr>
<tr>
<td>SrO</td>
<td>-3222</td>
<td>1635</td>
</tr>
<tr>
<td>BaO</td>
<td>-3034</td>
<td>1475</td>
</tr>
</tbody>
</table>

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### <Success>Question</Success>
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<p><strong>Question</strong>- What is kinetic lability ?</p>
<p><strong>Answer</strong>- They have easy pathways for decomposition and one such mechanism involves $\beta$-hydrogen elimination</p>

<p>$(\mathrm{Bu}_3 \mathrm{P}) \mathrm{CuCH}_2 \mathrm{CD}_2 \mathrm{C}_2 \mathrm{H}_5 \longrightarrow(\mathrm{Bu} \mathrm{P}) \mathrm{CuD}+\mathrm{CH}_2=\mathrm{CDC}_2 \mathrm{H}_5$</p>

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#### <Success>Diagonal relationship between Be and Al</Success>
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<ul>
<li>$Be^{2+}$ ionic radium ~31 pm; charge/size ratio = $Al^{3+}$</li>
<li>As a result they have similarities in their properties</li>
<li>Al forms an oxide film and as a result resistant to acid attack</li>
<li>Be does the same</li>
<li>Be(OH), dissolves in excess of alkali to form beryllate ion, Be(OH)</li>
</ul>

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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/chemistry-class-12-unit-07-chapter-01-some-p-block-elements-l-5_8-1wlbipddqua-140.jpg"></p>

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#### <Success>Diagonal relationship between Be and Al</Success>
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<ul>
<li>Al does the same</li>
<li>Chlorides of both Be and Al have bridged structures both the chlorides in monomeric form are strong lewis acids used in friedel craft reactions</li>
<li>Both have strong tendency to form complenes, $BeF_4^{2-}$ and $AlF_6^{3-}$</li>
</ul>


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