What is the VSEPR model for #"CH"_2"O"# ?
The VSEPR model predicts that CH₂O is trigonal planar with bond angles of about 120 °.
We must first draw the Lewis structure for CH₂O.
There are three electron regions around the central carbon atom.
The VSEPR model states that the electron regions around an atom spread out to make each one as far from the others as possible.
In formaldehyde, the central atom has three electron clouds emanating from it. The carbon atom has two single bonds to hydrogen and a double bond to oxygen.
For these clouds to be as far as possible from one another, they will form a plane containing the central atom. The bonds will emanate from the central atom at angles of about 120° to each other. The structure will be trigonal planar.
The central atom is in the centre of the triangle, with the ends of the electron clouds at the corners of the triangle. We classify CH₂O as an AX₃ molecule.
The actual bond angles are ∠HCH = 116 ° and ∠HCO = 122 °.