The Lewis dot structure for CH2F2, the chemical formula for difluoromethane, is a C in the center with lines on each side to the two H's and the two F's. Each H contains 3 pairs of dots around the unbonded sides.
In the Lewis structure, the C represents the carbon, the H represents the two hydrogen atoms, the F represents the two fluorine atoms, the dots represent electrons and the lines represent a bonded pair of electrons. Each fluorine atom contains seven valence electrons. This number can be determined by fluorine's column on the periodic table. Each carbon atom has four electrons, also shown by its column on the periodic table. To bond with two fluorine atoms, the carbon atom must create a single bond with each fluorine atom, using up its valence electrons. One of the seven valence electrons from the fluorine atoms bonds with the single electron from the carbon atom, leaving each fluorine atom with six remaining unbonded valence electrons. In the Lewis dot structure, these remaining electrons are represented by dots placed equally around the elements symbol. To double check the accuracy of the Lewis dot structure, students can count up all the electrons, counting each dot as one electron and each bond as two electrons. The number of electrons in the structure should equal the number of electrons in CH2F2.