chemistry-class-11-unit-11-chapter-04-some-p-block-elements-l-4-4-oi87v8gmqeq

### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Chemical reactivity of group 2 elements </primary>
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| Metal | $Be$ | $Mg$ | $Ca$ | $Sr$ | $Ba$ |
| -------- | -------- | -------- | -------- | -------- | -------- |
| Colour    | No     | No   | brick red   | Crimson red | Apple green |
| $\lambda$ in nm    |      |   | 662  | 650  | 554.5 |

- **Reactivity -**

- Air (oxygen), water, $H_2, N_2,$ halogens, reducing nature, behavior in liquid $NH_3$

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<footer style = "font-size: 18px">P block elements $\rightarrow$ Hydration enthalpy trend $\rightarrow$ <span style = "color:blue"> Chemical reactivity of group 2 elements </span> $\rightarrow$ Flame test $\rightarrow$ Chemical reactivity of group 2 elements </footer>

### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Flame test </primary>
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### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Chemical reactivity of group 2 elements </primary>
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- Smaller size compared to alkali metals, strongly hydrated, high lattice energy

- Be has different chemistry compared to $\mathrm{Mg}, \mathrm{Ca}, \mathrm{Sr}, \mathrm{Ba}$ and $\mathrm{Ra}$

- Free $\mathrm{Be}^{2+}$ does not exist, all its compounds are covalent or contain solvated ions such as $\left[\mathrm{Be}\left(\mathrm{H}_2 \mathrm{O}\right)_4\right]^{2+}$

- Many of the salts are less soluble in water, $K_2SO_4$ is soluble not $CaSO_4$ and $SrSO_4$

- $Be$ is a rare element, $Be_3Al_2Si_6O_{18}$ (Beryl)

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<footer style = "font-size: 18px">Chemical reactivity of group 2 elements $\rightarrow$ Flame test $\rightarrow$ <span style = "color:blue"> Chemical reactivity of group 2 elements </span> $\rightarrow$ Chemical reactivity of group 2 elements $\rightarrow$ Group 2 elements </footer>

### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Chemical reactivity of group 2 elements </primary>
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- $[Be(H_2O)_4]^{2+}$

- $Be_3Al_2Si_6O_{18} \xrightarrow {Na_2SiF_6} Na_2[BeF_4] \xrightarrow [{-NaF}]{NaOH} Be(OH)_2 \xrightarrow {(NH_4)_2HF_2} (NH_4)_2BeF_4 \xrightarrow {\Delta} BeF_2 \xrightarrow [{-MgF_2}]{Mg} Be$

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### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Chemical reactivity of group 2 elements </primary>
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| Oxide | Lattice E (KJ/mol) | M.P.$(^oC)$ |
| -------- | -------- | -------- |
| $BeO$    | -4298     | 2507     |
| $MgO$    | -3800     | 2800     |
| $CaO$    | -3419     | 1728     |
| $SrO$    | -3222     | 1635     |
| $BaO$    | -3034     | 1475     |
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- $Ca(OH)_2+H_2O_2+6H_2O \rightarrow CaO_2.8H_2O$

- $CaO+H_2O \rightarrow Ca(OH)_2,Mg^{2+}+2OH^- \rightarrow Mg(OH)_2$

- $Ba(OH)_2$  is the most stable and most soluble hydroxide

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### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Chemical reactivity of group 2 elements </primary>
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- $Ca(OH)_2+H_2O_2+6H_2O \rightarrow CaO_2.8H_2O$

- $CaO+H_2O \rightarrow Ca(OH)_2$

- $Mg^{2+}+2OH^- \rightarrow Mg(OH)_2$

- $M(OOCR)_2 \rightarrow $ normal salts

- $Be(OH)_2+RCOOH \rightarrow Be_4O(OOCR)_6$

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### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Group 2 elements </primary>
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- $3Mg+N_2 \xrightarrow {\Delta} Mg_3N_2$

- $Mg_3N_2+6H_2O \rightarrow 3Mg(OH)_2+2NH_3(aq)$
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### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
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- $3Mg+N_2 \xrightarrow {\Delta} Mg_3N_2$

- $Mg_3N_2+6H_2O \rightarrow 3Mg(OH)_2+2NH_3(aq)$

- The carboxylate salts of the metals $\mathrm{Mg}$ to $\mathrm{Ba}$ of the type $\mathrm{M}(\mathrm{OOCR})_2$ are all normal salts, however, $\mathrm{Be}(\mathrm{OH})_2$ reacts with $\mathrm{RCOOH}$ to give basic carboxylates, $\mathrm{Be}_4 \mathrm{O}(\mathrm{OOCR})_6$

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<footer style = "font-size: 18px">Chemical reactivity of group 2 elements $\rightarrow$ Group 2 elements $\rightarrow$ <span style = "color:blue"> Chemical reactivity of group 2 elements </span> $\rightarrow$ Reactivity of group 2 elements $\rightarrow$ Kinetic lability </footer>

### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Kinetic lability </primary>
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- They have easy pathways for decomposition and one such mechanism involves B-hydrogen elimination

- $(Bu_3P)CuCH_2CD_2C_2H_5 \rightarrow (Bu_3P)CuD+CH_2=CDC_2H_5$

- $\beta$ - Eliminations can also be reversible

- $Cp_2Nb(C_2H_4)C_2H_5 \xtofrom [{+C_2H_4}]{-C_2H_4} Cp_2Nb(C_2H_4)H$
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### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Chemical reactivity of group 2 elements </primary>
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### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Organomagnesium compounds </primary>
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<footer style = "font-size: 18px">Chemical reactivity of group 2 elements $\rightarrow$ Organomagnesium compounds $\rightarrow$ <span style = "color:blue"> Organomagnesium compounds </span> $\rightarrow$ Diagonal relationship between Be \& Al $\rightarrow$ Ask yourself a question </footer>

### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Diagonal relationship between Be \& Al </primary>
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- $\mathrm{Be}^{2+}$ ionic radium $\approx$31 pm ; charge  size ratio $={Al}^{3+}$
- As a result they have similarities in their properties
- Al forms an oxide film and as a result resistant to acid attack
- Be does the same
- $\mathrm{Be}(\mathrm{OH})_2$ dissolves in excess of alkali to form beryllate ion, $\left[\mathrm{Be}(\mathrm{OH})_4\right]^{2-}$ Al does the same
- Chlorides of both Be and Al have bridged structures
- Both the chlorides in monomeric form are strong Lewis acids
- Used in Friedel Craft reactions
- Both have strong tendency to form complexes, $\mathrm{BeF}_4^{2-}$ and $\mathrm{AlF}_6^{3-}$

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<footer style = "font-size: 18px">Organomagnesium compounds $\rightarrow$ Organomagnesium compounds $\rightarrow$ <span style = "color:blue"> Diagonal relationship between Be \& Al </span> $\rightarrow$ Ask yourself a question $\rightarrow$ Chemical reactivity of group 2 elements </footer>

### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Ask yourself a question </primary>
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- Suggest a structure for a dimer of $\mathrm{BeCl}_2$ and explain how its formation illustrates $\mathrm{BeCl}_2$ acting as a Lewis acid?
- Reaction of a magnesium carbide with water gives propyne Suggest a formulation of the carbide, and give an example of a common gaseous molecule with which the carbide ion is isoelectronic
- Why does the solubility of alkaline earth metal hydroxides in water increase down the group?

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<footer style = "font-size: 18px">Organomagnesium compounds $\rightarrow$ Diagonal relationship between Be \& Al $\rightarrow$ <span style = "color:blue"> Ask yourself a question </span> $\rightarrow$ Chemical reactivity of group 2 elements $\rightarrow$ Chemical reactivity of group 2 elements </footer>

### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Chemical reactivity of group 2 elements </primary>
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- $Mg_2C_3$ $CH_3-C \equiv CH$

- $Mg_2C_3+2H_2O \rightarrow CH_3-C \equiv CH+2MgO$

- $Mg = C = C = C = Mg$ $CO_2$

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### <Success style="font-size:25px"> Some P Block Elements L-4 </Success>
### <primary style="font-size:24px"> Summary on group 2 elements </primary>
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- The +2 oxidation dominates the chemistry of Group 2 elements
- All alkaline earth metals show low I and II ionization enthalpies and are most electropositive elements in the periodic table
- $\mathrm{Be}^{2+}$ ion due to its smaller size forms either covalent compounds or contain solvated ions
- The Group 2 metals form more stable coordination complexes compared to the Group 1 metals
- Alkaline earth metals form basic oxides with berylium due to its smaller size, $\mathrm{BeO}$ is amphoteric

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