A 1:1 ratio in forming compounds indicates that two elements are combined in equal proportions. The discussion involves combining elements from two columns, with the goal of identifying three chemical compounds formed from these elements. It is clarified that the question may allow for combinations of one element from each column or potentially two from one column and one from the other. Understanding the valences of the elements is crucial, as only those with equal but opposite valences can combine in a 1:1 ratio. Knowledge of chemical symbols and existing compounds aids in the formation of these compounds.