Homework Question 4.73

[404975170]

For Question 4.73, how do lone pairs affect bond angles? Specifically when comparing CH2^2- and CH3^- since they are both less than 109.5 degrees but CH3^- is slightly bigger.

[Komal Prakash 1H]

Lone pairs exert a force on the bonds that pushes them further to create an angle less that 109.5 degrees. Lone-lone pair repulsion is the strongest, followed by lone-bonding pair, and then bonding to bonding pair. In the case of CH2^2- and CH3^-, CH2^2- has an extra lone pair in comparison to CH3^-. Thus, there will be a stronger cumulative force from the lone pairs exerted on the C-H bonds in the CH2^2- than in the CH3^- molecule. Thus, the bond angle in CH2^2- will be more smaller than 109.5 than the bond angle in CH3^- .