chemistry-class-11-unit-04-chapter-06-chemical-bonding-molecular-structure-l-6-7-gs3vpkalvpe

### <Success style="font-size:25px"> Chemical Bonding Molecular Structure L-6 </Success>
### <primary style="font-size:24px"> Energy level of molecules </primary>
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- Because of the number of interactions and the electron electron repulsion present in the molecule , the energy level cannot be calculated 
- Then , we must go for an approximation method
- Linear combination of atomic orbital - LCAO is one of the approximation method  
- $H_2^{+}$($H_A$ and $H_B$) - there is only one electron
 - The atomic orbitals of $H_A$ can be described by wave function $\phi_A$
 - The atomic orbitals of $H_B$ can be described by wave function $\phi_B$
 - If the electron is present near the $H_A$ then the molecule can be described by $\phi_A$
 - If the electron is present near the $H_B$ then the molecule can be described by $\phi_B$
 - If the electron is present in between the $H_A$ and $H_B$ then the molecule can be described by $\phi_A \pm \phi_B$
 
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<footer style = "font-size: 18px"> $\rightarrow$ Chemical bonding molecular structure $\rightarrow$ <span style = "color:blue"> Energy level of molecules </span> $\rightarrow$ Molecular orbitals $\rightarrow$ Bonding and antibonding molecular orbital </footer>

### <Success style="font-size:25px"> Chemical Bonding Molecular Structure L-6 </Success>
### <primary style="font-size:24px"> Molecular orbitals </primary>
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- Bonding 
 - $\psi_B$=$\phi_A+\phi_B$
 - $\phi_A$ $and$ $\phi_B$ reinforce each other
 - Lower in energy
- Antibonding
 - $\psi_a$=$\phi_A-\phi_B$
 - $\phi_A$ $and$ $\phi_B$ cancel each other
 - Higher in energy

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<footer style = "font-size: 18px">Chemical bonding molecular structure $\rightarrow$ Energy level of molecules $\rightarrow$ <span style = "color:blue"> Molecular orbitals </span> $\rightarrow$ Bonding and antibonding molecular orbital $\rightarrow$ Conditions for the formation of molecular orbitals </footer>

### <Success style="font-size:25px"> Chemical Bonding Molecular Structure L-6 </Success>
### <primary style="font-size:24px"> Bonding and antibonding molecular orbital </primary>
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- $\Delta$E - bond energy of H-H bond
- The bonding molecular orbital for $H_2$ is $\sigma$ while the antibonding is $\sigma^*$
- The same way -  $\sigma \hspace{1mm} , \sigma^* \hspace{1mm}, \pi \hspace{1mm} , \pi^* \hspace{1mm} , \delta $

- $\phi_A+\phi_B$ Bonding
- Cylindrically symmetrical

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<footer style = "font-size: 18px">Energy level of molecules $\rightarrow$ Molecular orbitals $\rightarrow$ <span style = "color:blue"> Bonding and antibonding molecular orbital </span> $\rightarrow$ Conditions for the formation of molecular orbitals $\rightarrow$ Overlapping of orbitals </footer>

### <Success style="font-size:25px"> Chemical Bonding Molecular Structure L-6 </Success>
### <primary style="font-size:24px"> Conditions for the formation of molecular orbitals </primary>
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- Energy of orbitals must be almost equal
- Symmetry of orbitals must be the same 
- Overlapping must be greater

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<footer style = "font-size: 18px">Molecular orbitals $\rightarrow$ Bonding and antibonding molecular orbital $\rightarrow$ <span style = "color:blue"> Conditions for the formation of molecular orbitals </span> $\rightarrow$ Overlapping of orbitals $\rightarrow$ Molecular orbital theory </footer>

### <Success style="font-size:25px"> Chemical Bonding Molecular Structure L-6 </Success>
### <primary style="font-size:24px"> Overlapping of orbitals </primary>
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- The combination of $P_x$ and $P_x$ orbital will form $\pi$ bond -  $P_x+P_x$ = $\pi$ bond , or 
- The combination of $P_y$ and $P_y$ orbital will form $\pi$ bond -  $P_y+P_y$ = $\pi$ bond

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<footer style = "font-size: 18px">Bonding and antibonding molecular orbital $\rightarrow$ Conditions for the formation of molecular orbitals $\rightarrow$ <span style = "color:blue"> Overlapping of orbitals </span> $\rightarrow$ Molecular orbital theory $\rightarrow$ Molecular orbital diagram </footer>

### <Success style="font-size:25px"> Chemical Bonding Molecular Structure L-6 </Success>
### <primary style="font-size:24px"> Molecular orbital theory </primary>
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- Number of electrons in bonding orbital is $N_b$

- Number of electrons in anti - bonding orbital is $N_b$

- Bond order(b.o) = $\frac{N_b-N_a}{2}$

- Bond order should be +ve for stable molecule

- if , bond order = 0 (unstable molecule)

- bond order = 1 single bond

- bond order = 2 double bond

- bond order = 3 triple bond

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<footer style = "font-size: 18px">Conditions for the formation of molecular orbitals $\rightarrow$ Overlapping of orbitals $\rightarrow$ <span style = "color:blue"> Molecular orbital theory </span> $\rightarrow$ Molecular orbital diagram $\rightarrow$ Molecular orbital diagram </footer>

### <Success style="font-size:25px"> Chemical Bonding Molecular Structure L-6 </Success>
### <primary style="font-size:24px"> Molecular orbital diagram </primary>
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- $H_2$ 
 - B.O = $\frac{2-0}{2}$ = 1
- $He_2$
 - $(\sigma_{1s})$ $(\sigma^*_{1s})^2$
 - B.O = $\frac{2-2}{2}$ = 0
- $He_2$ is unstable

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<footer style = "font-size: 18px">Overlapping of orbitals $\rightarrow$ Molecular orbital theory $\rightarrow$ <span style = "color:blue"> Molecular orbital diagram </span> $\rightarrow$ Molecular orbital diagram $\rightarrow$ Thank you </footer>

### <Success style="font-size:25px"> Chemical Bonding Molecular Structure L-6 </Success>
### <primary style="font-size:24px"> Molecular orbital diagram </primary>
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- $Li_2$ 
 - $1s^2 2s^1$
 - $(\sigma_{1s})^2$ $(\sigma^*_{1s})^2$
 - B.O = $\frac{2-0}{2}$ = 1
 - Li-Li (stable molecule )

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<footer style = "font-size: 18px">Molecular orbital theory $\rightarrow$ Molecular orbital diagram $\rightarrow$ <span style = "color:blue"> Molecular orbital diagram </span> $\rightarrow$ Thank you $\rightarrow$  </footer>