chemistry-class-11-unit-10-chapter-01-s-block-elements-l-4-qc9p3peq8a

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Alkali metal elements </primary>
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- Electronic configuration is $ns^1$

- Oxidation state +1

- With water they readily form hydroxides which are strongly alkaline in nature, hence the name alkali metals

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|  1 |  2 |
| -------- | -------- | 
| H    |     | 
| Li    | Be     | 
| Na    | Mg     |
| K    | Ca     |
| Rb    | Sr     |
| Cs    | Ba     |
| Fr    | Ra     |

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<footer style = "font-size: 18px"> $\rightarrow$ S-block elements $\rightarrow$ <span style = "color:blue"> Alkali metal elements </span> $\rightarrow$ Alkali metal elements $\rightarrow$ Flame test </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Flame test </primary>
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| Metal | Li | Na | K | Rb |Cs |
| -------- | -------- | -------- | -------- | -------- |-------- |
| Colour    | Crimson     | Golden yellow   | Violet  | Red violet |Blue |
| $\lambda$in nm    | 670.8     | 589.2  | 766.5  | 780  |455.5 |

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

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Chemical reactivity </primary>
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- Highly reactive due to their large size and low IE and reactivity increases down the group towards $O_2$ on exposure to air, they tarnish due to the formation of oxides which in turn react with moisture to form hydroxides

- $4Li+O_2 \rightarrow 2Li_2O$ Oxide

- $2Na+O_2 \rightarrow Na_2O_2$ peroxide

- $M+O_2 \rightarrow MO_2$ superoxide(M=K,Rb,Cs)

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<footer style = "font-size: 18px">Flame test $\rightarrow$ Chemical reactivity $\rightarrow$ <span style = "color:blue"> Chemical reactivity </span> $\rightarrow$ Chemical reactivity $\rightarrow$ Compounds with oxygen </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Compounds with oxygen </primary>
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| Metal | Salt | Anion | Hydrolysis product(s) of salt |
| -------- | -------- | -------- | -------- |
| Li    | $Li$     | $O^{2-}$(oxide)   | $OH^-$   |
| Na    | $Na_2O_2,Na_2O$     | $O^{2-}_2$(peroxide)  | $OH^-,H_2O_2$   |
| K,Rb,Cs    | $MO_2$     | $O^-_2$(superoxide) | $OH^-,H_2O_2,O_2$    |

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<footer style = "font-size: 18px">Chemical reactivity $\rightarrow$ Chemical reactivity $\rightarrow$ <span style = "color:blue"> Compounds with oxygen </span> $\rightarrow$ Compounds with oxygen $\rightarrow$ Compounds with oxygen </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Compounds with oxygen </primary>
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- $Na_2O+H_2O \rightarrow 2NaOH$

- $Na_2O_2+H_2O \rightarrow Na_2O+H_2O_2$

- $6M+2MNO_2 \rightarrow 4M_2O+N_2$

- $M+O_3 \rightarrow MO_3$ ozanide salts $M_2S_x$

- $2Na+S \rightarrow Na_2S$

- $2Na_2S+S_8 \rightarrow 2Na_2S_5$

- $4Na+5Te \rightarrow Na_2Te_2+Na_2Te_3$

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<footer style = "font-size: 18px">Chemical reactivity $\rightarrow$ Compounds with oxygen $\rightarrow$ <span style = "color:blue"> Compounds with oxygen </span> $\rightarrow$ Compounds with oxygen $\rightarrow$ Compounds with halogens </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Radius ratio rule </primary>
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- The structure adopted by a salt MX can be predicted by considering the relative sizes of the cation (radius r) and anion (r), the so-called radius ratio rule

| $r^+/r^-$ | structure type | 
| -------- | -------- | 
| 0.225-0.414    | ZnS(sphalerite)     | 
| 0.414-0.732    | Nacl     | 
| > 0.732    | CsCl     |

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<footer style = "font-size: 18px">Compounds with oxygen $\rightarrow$ Compounds with halogens $\rightarrow$ <span style = "color:blue"> Radius ratio rule </span> $\rightarrow$ Radius ratio rule $\rightarrow$ Radius ratio rule </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Radius ratio rule </primary>
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* Radius ratio rules provide a reasonably general means of assessing the likely structure adopted by an ionic solid, but give incorrect predictions when, there is a significant covalent bonding

* The radius ratio is near borderline lonic radii are not known accurately, the values vary with the coordination number (how many nearest neighbour ions) of the ion

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<footer style = "font-size: 18px">Compounds with halogens $\rightarrow$ Radius ratio rule $\rightarrow$ <span style = "color:blue"> Radius ratio rule </span> $\rightarrow$ Radius ratio rule $\rightarrow$ Radius ratio rule </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Simple coordination complexes </primary>
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- Stable complexes are formed by multidentate ligands which can encapsulate the metal ions

- Example crown ethers, cryptands

- $M^+ + cryptand \rightleftharpoons [M(cryptand)]^+$

- Stability of these complexes increases if the size of $M^+$ matches the cavity size

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<footer style = "font-size: 18px">Hydrides $\rightarrow$ Structure of alkly(methyl) lithium $\rightarrow$ <span style = "color:blue"> Simple coordination complexes </span> $\rightarrow$ Simple coordination complexes $\rightarrow$ Crown ethers & group </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Similarity between li and mg </primary>
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- Diagonal relationship is the specialty of the main group elements

- Li shows many similarities to Mg rather than to the "heavier alkali metals"(Na,K etc)

- $Li \rightarrow Li_2O,\hspace{3mm} Mg \rightarrow MgO \hspace{3mm} Na \rightarrow Na_2O_2$

- $Li_2CO_3 \rightarrow Li_2O,\hspace{3mm} MgCO_3 \rightarrow MgO \hspace{3mm} Na_2CO_3$ is stable

- $[Li(NH_3)_4]^+ \hspace{3mm} [Mg(NH_3)_4]^{2+}$

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<footer style = "font-size: 18px">Simple coordination complexes $\rightarrow$ Crown ethers & group $\rightarrow$ <span style = "color:blue"> Similarity between li and mg </span> $\rightarrow$ Uses of alkali metals & their compounds $\rightarrow$ Uses of alkali metals & their compounds </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Uses of alkali metals & their compounds </primary>
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* Li is used in metal alloys with lead WHITE METALS bearings for motor engines
- with Al for aircraft parts with Mg armour plates in thermonuclear reactions in electrochemical reactions

* Na-Pb alloy in making $PbMe_4$ and $PbEt_4$ liquid sodium as coolant in fast breeder nuclear reactors

* K plays vital role in biological system

* KCl in fertilizers, KOH in manufacture of soft soap
- for CO₂ absorption

* Cs is used in photoelectric cells

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<footer style = "font-size: 18px">Crown ethers & group $\rightarrow$ Similarity between li and mg $\rightarrow$ <span style = "color:blue"> Uses of alkali metals & their compounds </span> $\rightarrow$ Uses of alkali metals & their compounds $\rightarrow$ Uses of alkali metals & their compounds </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Uses of alkali metals & their compounds </primary>
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* Sodium carbonate $(Na_2CO_2)$ washing soda

* Sodium bicarbonate $NaHCO_3$, baking soda - reacts with acidic components to release $CO_2$, which causes expansion of the batter in bakery products giving characteristic texture and grain

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<footer style = "font-size: 18px">Similarity between li and mg $\rightarrow$ Uses of alkali metals & their compounds $\rightarrow$ <span style = "color:blue"> Uses of alkali metals & their compounds </span> $\rightarrow$ Uses of alkali metals & their compounds $\rightarrow$ Ask yourself a question </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Ask yourself a question </primary>
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*  What is the oxidation state of Na in $NaO_2$ or $Na_2O_2$

*  In the gas phase the alkali metals form dimers $M_2$ Draw a MO diagram for $M_2$ molecule

*  How would you synthesize (i) $NaClO_4$ starting from $Na_2CO_3$, and (ii) $CsClO_4$

*  Assuming the following ionic radii (in pm) $[Li^+ 74, Cs^+ 167, F^- 133, I^- 220]$ predict what structure type will be adopted by the following alkali metal salts

- (a) Csl (b) Lif

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<footer style = "font-size: 18px">Uses of alkali metals & their compounds $\rightarrow$ Uses of alkali metals & their compounds $\rightarrow$ <span style = "color:blue"> Ask yourself a question </span> $\rightarrow$ Ask yourself a question $\rightarrow$ Ask yourself a question </footer>

### <Success style="font-size:25px"> S Block Elements L-4 </Success>
### <primary style="font-size:24px"> Summary on group 1 elements </primary>
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* Group 1 elements and their compounds follow the periodic properties and trends with very least or no variations

* Alkali metals are highly reactive, and form basic oxides and water soluble halides, containing $M^+$ cations

* Among alkali metal compounds, whether hydrides, oxides, halides or organometallic compounds, ionic properties dominate the chemistry

* However, lithium with its small size, shows partial covalent character in its many compounds and shows resemblance to magnesium (diagonal relationship)

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<footer style = "font-size: 18px">Ask yourself a question $\rightarrow$ Ask yourself a question $\rightarrow$ <span style = "color:blue"> Summary on group 1 elements </span> $\rightarrow$ Thank you $\rightarrow$  </footer>