Hey there! In a regular CF4 molecule, we have 4 valence electrons from carbon and 7 valence electrons from each of the 4 fluorine atoms, giving us a total of 4 + (4 x 7) = 32 valence electrons. Then, when CF4 gains an extra electron and becomes the CF4- ion, it ends up with a total of 32 + 1 = 33 valence electrons.
