If the reading on an electric meter in December was 2345 kilowatt-hours and the reading in January was 3456 kilowatt-hours, how much electrical energy was used in the one-month
period between the December and January readings?

Is there any opitions? if you have the periodic table, the noble gases are 8a family, the halogen are the 7a family, and the nonmetal are  carbon, nitrogen, phosphorus, oxygen, sulfur, selenium, fluorine, chlorine, bromine, iodine and astatine.