Chemistry Chemical Bonding and Molecular Structure

Kindly consider the following figure

As bond order is increasing it implies bond strength is increasing. As bond order is increasing it implies bond strength is increasing.

Total number of electron in Ti = 22
Total number of electron in Ti? = 22 – 4 = 18 So EAN value of Ti = 18 + 12 + 4 = 34

$N_{2}O,C_2{H}_2,C{O}_2,C_3{O}_2,Be{F}_2$

If hunds rule is followed

${N_2}^{-2}:\sigma 1s^2{\sigma }^{*}1s^2\sigma 2s^2{\sigma }^{*}2s^2\sigma 2{p_z}^2\pi 2{p^2}_x\pi 2{p_y}^2{\pi }^{*}2{p_x}^1{\pi }^{*}2{p_y}^1$            

If Hunds rule is not followed

${N_2}^{-2}:\sigma 1s^2{\sigma }^{*}1s^2\sigma 2s^2{\sigma }^{*}2s^2\sigma 2{p_z}^2\pi 2{p^2}_x\pi 2{p_y}^2{\pi }^{*}2{p_x}^2$            

Number of electrons in

$P{H}_3=15+3=18$  

$B_2{H}_6=5*2+6=16$  

$\begin{array}{l}CC{l}_4=6+17*4=6+68=74\\ N{H}_3=7+1*3=10\\ LiH=3+1=4\\ BC{l}_3=5+17*3=56\end{array}$  

$B_2{H}_6\&BC{l}_3$  are e^- deficient molecules. B₂H₆ is dimer of BH₃, both compound has 6e^- only.

Bond strength $\propto$  Bond order

$N_2\to {\sigma }_{1s}^2{\sigma }_{1s}^{*2}{\sigma }_{2s}^2{\sigma }_{2s}^{*2}{\pi }_{2px}^2\equiv {\pi }_{2py}^2{\sigma }_{2pz}^2$  

$O_2\to {\sigma }_{1s}^2{\sigma }_{1s}^{*2}{\sigma }_{2s}^2{\sigma }_{2s}^{*2}{\sigma }_{2pz}^2{\pi }_{2px}^2\equiv {\pi }_{2py}^2{\pi }_{2px}^{*1}\equiv {\pi }_{2py}^{*1}$

$C_2\to {\sigma }_{1s}^2{\sigma }_{1s}^{*2}{\sigma }_{2s}^2{\sigma }_{2s}^{*2}{\pi }_{2px}^2\equiv {\pi }_{2py}^2$  

$B_2\to {\sigma }_{1s}^2{\sigma }_{1s}^{*2}{\sigma }_{2s}^2{\sigma }_{2s}^{*2}{\pi }_{2px}^1\equiv {\pi }_{2py}^1$  

NO ® Number of electron = 7 + 8 = 15

B.O. Similar to  $N_2^{-}$  

$N_2^{-}\to {\sigma }_{1s}^2{\sigma }_{1s}^{*2}{\sigma }_{2s}^2{\sigma }_{2s}^{*2}{\pi }_{2px}^2\equiv {\pi }_{2py}^2{\sigma }_{2pz}^2{\pi }_{2px}^{*1}\equiv {\pi }_{2py}^{*}$  

B.O. of N₂ = 3     B.O of C₂ = $\frac{8-4}{2}=2$  

Removal of e^- form antibonding molecular orbital increases bond order.

In NO & O₂ has valance e^- in p orbital.

E.C = σ1s² σ1s² σ2s² σ2s² σ2p? ² π2p? ² = π2p? ² π2p? ² = π2p? ²
Total electrons in BMO = 10

Cl? > F? > O? > N?
3p-3p 2p-2p B.O=2 B.O=3

N? , I? , NO? are linear.