therefore each carbon atom in a molecule or ion contributes four electrons each hydrogen atom one electron and each
oxygen atom six electron the total number of valence electron equals tha sum of the valence electron on all of the atoms in the species being studied for ch2o this total would be 4+ 2x1 +6 or 12 valence electrons if we are working with an ion we add one electron for each nagative charege or subtract one for each positive charge on the ion