chemistry-class-11-unit-03-chapter-02-classification-of-elements-periodicityin-properties-l-2-2-sqxkdlwvkby

### <Success style="font-size:25px"> CLASSIFICATION OF ELEMENTS AND PERIODIC PROPERTIES L-2 </Success>
### <primary style="font-size:24px"> Structure and bonding aspects </primary>
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- **Lewis structures**
- 1916 proposed the theory of bonding at university of california at berkeley
- Added information about electrons in the periodic table
- Worked on purification of heavy water
- Proposed acid-base theory (lewis acid and lewis base concept)
- Worked in the field of photochemistry
- Nominated 41 times for nobel prize
- Found dead on march 23,1946 in his laboratory
- At that time he was working with hydrogen cyanide

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<footer style = "font-size: 18px">Classification of elements $\rightarrow$  $\rightarrow$ <span style = "color:blue"> Structure and bonding aspects </span> $\rightarrow$ Lewis structures $\rightarrow$ Lewis structures </footer>

### <Success style="font-size:25px"> CLASSIFICATION OF ELEMENTS AND PERIODIC PROPERTIES L-2 </Success>
### <primary style="font-size:24px"> Lewis structures </primary>
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- Once we have determined the number of total valence electrons we can start distributing them throughout the molecule
- When we represent electrons they will be in pairs (since an orbital holds 2 electrons)
- Electron pairs can be represented with 2 dots or a solid line
- So let us look into some molecules or ions

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<footer style = "font-size: 18px"> $\rightarrow$ Structure and bonding aspects $\rightarrow$ <span style = "color:blue"> Lewis structures </span> $\rightarrow$ Lewis structures $\rightarrow$ Lewis structures </footer>

### <Success style="font-size:25px"> CLASSIFICATION OF ELEMENTS AND PERIODIC PROPERTIES L-2 </Success>
### <primary style="font-size:24px"> Lewis structures </primary>
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- $ClO_2 ^{-}$

- $s^2 p^5 = 7$

- $20 \quad s^2 p^6 = 6 \times 2 = 12$

- $+1 = 20e - 4 = 16e$

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<footer style = "font-size: 18px">Structure and bonding aspects $\rightarrow$ Lewis structures $\rightarrow$ <span style = "color:blue"> Lewis structures </span> $\rightarrow$ Lewis structures $\rightarrow$ Lewis structures </footer>

### <Success style="font-size:25px"> CLASSIFICATION OF ELEMENTS AND PERIODIC PROPERTIES L-2 </Success>
### <primary style="font-size:24px"> Failures of the lewis model </primary>
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- A number of molecules with odd numbers of electrons exist (no octet) example - NO
- An atom may not have enough electrons to complete its octet without having formal charges example -  compounds of group 13 elements with $s^2 p^1$ configuration , $\mathrm{BF}_3$
- A central atom having more than 8 electrons example - $\mathrm{SF}_6$
$\mathrm{O}_2$ is paramagnetic
- Geometry and shape of the molecules - No information

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<footer style = "font-size: 18px">Lewis structures $\rightarrow$ Lewis structures $\rightarrow$ <span style = "color:blue"> Failures of the lewis model </span> $\rightarrow$ Valence shell electron pair repulsion theory (VSEPR) $\rightarrow$ Structure and bonding aspects </footer>

### <Success style="font-size:25px"> CLASSIFICATION OF ELEMENTS AND PERIODIC PROPERTIES L-2 </Success>
### <primary style="font-size:24px"> Valence shell electron pair repulsion theory (VSEPR) </primary>
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- **Predicting molecular geometries**
- Draw the lewis structure
- Count the total number of bonding regions and lone pairs around the central atom
- Steric number [SN] = number of attached atom  + number of lone pairs
- Arrange the bonding regions and lone pairs in one of the standard geometries to minimize $\mathrm{e}^{-}-\mathrm{e}^{-}$repulsion
- Multiple bonds count as a single bonding region

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<footer style = "font-size: 18px">Lewis structures $\rightarrow$ Failures of the lewis model $\rightarrow$ <span style = "color:blue"> Valence shell electron pair repulsion theory (VSEPR) </span> $\rightarrow$ Structure and bonding aspects $\rightarrow$ Structure and bonding aspects </footer>

### <Success style="font-size:25px"> CLASSIFICATION OF ELEMENTS AND PERIODIC PROPERTIES L-2 </Success>
### <primary style="font-size:24px"> Structure and bonding aspects </primary>
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- $IF_4^- \quad 7+4+1=\frac{12}{2}$ = 6 SN  (4 bond pair  and 2 lone pair)
 
- $IF_5 = 7+5 = 12$, 6 SN  (5 bond pair and 1 lone pair)

- $IF_7 \quad 7+7=14$, 7 SN , (pentagonal bipramidal)

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<footer style = "font-size: 18px">Structure and bonding aspects $\rightarrow$ Structure and bonding aspects $\rightarrow$ <span style = "color:blue"> Structure and bonding aspects </span> $\rightarrow$ Structure and bonding aspects $\rightarrow$ Structure and bonding aspects </footer>

### <Success style="font-size:25px"> CLASSIFICATION OF ELEMENTS AND PERIODIC PROPERTIES L-2 </Success>
### <primary style="font-size:24px"> Valence bond theory </primary>
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- Let us consider carbon atom
- Its electronic configuration is $s^2 p^1$ during hybridization its electron configuration will be $s^1 p^2$ as shown below
- The hybridization of a s and two p orbitals led to $3 s p^2$ hybrid orbitals for bonding
- Compounds involving $sp^2$ hybrid orbitals
 - $BF_3 , ~ CO_3^{2-}, ~ H_2CO$
 - $ H_2C=CH_2, ~ NO_3^- , ~ $etc

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<footer style = "font-size: 18px">Structure and bonding aspects $\rightarrow$ Structure and bonding aspects $\rightarrow$ <span style = "color:blue"> Valence bond theory </span> $\rightarrow$ Valence bond theory $\rightarrow$ Valence bond theory </footer>

### <Success style="font-size:25px"> CLASSIFICATION OF ELEMENTS AND PERIODIC PROPERTIES L-2 </Success>
### <primary style="font-size:24px"> Valence bond theory </primary>
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<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/994d9a0d-5844-4028-726c-aa8766e43700/public" >
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<footer style = "font-size: 18px">Structure and bonding aspects $\rightarrow$ Valence bond theory $\rightarrow$ <span style = "color:blue"> Valence bond theory </span> $\rightarrow$ Valence bond theory $\rightarrow$ Valence bond theory </footer>

### <Success style="font-size:25px"> CLASSIFICATION OF ELEMENTS AND PERIODIC PROPERTIES L-2 </Success>
### <primary style="font-size:24px"> Valence bond theory </primary>
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- $X-P-X \quad POX_3$

- $X = Br \quad 104.1^o$

- $X = Cl \quad 103.3^o$

- $X = F  \quad 101.3^o$

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<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/5d31e7a3-c2ed-426a-1be4-2c252af8f100/public" width="100%">
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<footer style = "font-size: 18px">Valence bond theory $\rightarrow$ Valence bond theory $\rightarrow$ <span style = "color:blue"> Valence bond theory </span> $\rightarrow$ Valence bond theory $\rightarrow$ Valence bond theory </footer>