Answer to Question #107694 in Chemistry for A

Question

Hi,May I please ask the molecule difluoromethane(CH2F2) which is used as a refrigerant called R-32:
1)Based on the structure,how many electron domains surround the C atom in the molecule?
2)Would the molecule have nonzero dipole moments?yes/no
Thanks

Answer 1

In difluoromethane molecule CH₂F₂, the central atom is carbon. If you look in the Periodic Table, you can find that there are 4 electrons in the valence shell of carbon atom. Fluorine (1 electron needed to complete the valence shell) and hydrogen (1 electron needed to complete the valence shell) atoms can share one electron each. Therefore, in CH₂F₂, carbon is surrounded by 4 electron domains: two electron pairs shared with two fluorines and two electron pairs shared with two hydrogens. Therefore, its electron domain geometry is tetrahedral. However, as the bonds with fluorine and with hydrogen are not equivalent (as hydrogen and fluorine are different elements), the bond angles will deviate from ideal 109.5°.

The electronegativity of the constituting elements increases in the following row: H (2.20)< C(2.55) < F(3.98). Although the structure is nearly symmetric ( bent), the bonds C-H and C-F are not equivalent, and the difluoromethane molecule will have a nonzero dipole moment:

Answer: 1) 4 electron domains surround the C atom in the CH₂F₂ molecule.

2) Yes, the molecule would have a nonzero dipole moment.