The formula for the compound formed by tin and phosphorus can be predicted by considering the valencies of the two elements. Tin (Sn) belongs to Group 14 of the periodic table and has a valence of +4, while phosphorus (P) belongs to Group 15 and has a valence of +3 or -3.

To achieve a neutral overall charge in the compound, the valencies of tin and phosphorus must balance each other. This can be achieved by combining one tin atom with four phosphorus atoms, resulting in the formula SnP4.

Therefore, the predicted formula for the compound formed by tin and phosphorus is SnP4.