HCH bond angles 4.73

[Semi Yoon]

For each of the following species: CH3 ; CH4; CH3 ; CH2; CH22 ; CH22, identify each as a radical or not. How would you rank them in order of increasing HCH bond angles?

[Kevin Tang 4L]

None of them are radicals because all of them end in an even number.

In increasing order, it goes CH2 (2-), CH3(-), CH4, CH2, CH3 (+), CH2 (2+),
This is because of the molecular geometry.
CH2 (2-) is bent, sp3 hybridized which means its going to have angle less than 120 (much lower because of two lone pairs)
CH3(-) is trigonal pyramidal, sp3 hybridized
CH4 is tetrahedral, sp3 hybridized, angle of 109.5
CH2 is bent sp2 hybridized, which means its going to have an angle less than 120 but its not going to be as big as the CH2(2-) because it only has one lone pair.
CH3 (+) is trigonal planar sp2 hybridized, angle of 120
CH2 (2+) is linear, sp hybridized, angle of 180.

Hope this helps.

[Moryel Yashar 1J]

Since all of these species are expected to be diamagnetic, none are radicals.

The Lewis structure of each species will help determine the order of increasing H-C-H bond angle.

The molecular shape and bond angle of each species is as follows: CH3 + is trigonal planar (120 degrees); CH4 is tetrahedral (109.5 degrees); CH3 - is trigonal pyramidal (slightly less than 109.5 degrees); CH2 is bent (slightly less than 120 degrees); CH2 2+ is linear (180 degrees); CH2 2- is bent (less than 109.5 degrees but more so than CH3 - because of the presence of two lone pairs).

Therefore, the order of increasing H-C-H bond angle will be CH2 2- < CH3 - < CH4 < CH2 < CH3 + < CH2 2+