CHEMISTRY COMMUNITY

Can someone confirm that my reasoning is correct for why "Angle b is expected to be around 109.5°?"

I understand why angles a and c are expected to be approximately 120° (because the VSEPR geometry is trigonal planar). So we must assume that the O has 2 pairs of lone pairs (to complete the octet) and therefore it has 4 regions of electron density with 2 lone pairs, ergo the shape is bent and the angles are <109.5°? Thanks.

Looks good to me! :)

Exactly. Typically, if a Lewis structure omits lone pairs, we must fill them in ourselves. Since the oxygen has two bonds, we can assume that it has two lone pairs, since oxygen has 6 shareable valence electrons and in this molecule has a formal charge of zero. Thus, with a VSEPR equation of AX2E2 and four areas of electron density, we can come to the conclusion that this oxygen has a tetrahedral election geometry with bond angles of less than 109.5 degrees, since its molecular shape (bent) has two lone pairs that push on the atoms, making the bond angles slightly less than 109.5 degrees.