ClF4 is the chemical formula for tetrafluorochlorate. Chlorine has a valence electron of 7 in its valence shell. Each of the electron is to be paired with another electron from the second atom, fluorine. Since there are only 4 fluorine atoms, 4 of the atoms of chlorine will bond to 4 fluorine atoms. Then, we are left with only 3 atoms. Two atoms will be paired with each other. One is the unpaired.
The words that would complete the sentence is one (1) and two (2).
