Once you have filled in all the gaps on a separate sheet of paper, enter the four missing element symbols in the first row of the table into the answer box below. You can open the first hint to view a video that steps you through filling in the first column of the table. Enter the four missing symbols for the first row of the table from left to right, separated by commas, into the answer box below. Use the stacked super/subscripts button (available in the templates button menu above the answer entry box) to enter the symbols in the following form: mass numberatomic number Symbol, or for example, 3517Cl .