Final answer:
The formula for a compound formed by barium and phosphorus is Ba3P2, which balances out the +2 charge of barium ions with the -3 charge of phosphorus ions.
Step-by-step explanation:
The formula for the binary compound formed between barium and phosphorus can be predicted by balancing the charges of the ions that each element forms.
Barium (Ba) tends to form a Ba2+ ion, while phosphorus (P) tends to form a P3- ion in ionic compounds.
To achieve a neutral compound, the charges must be balanced, therefore for every two barium ions (each with a +2 charge), three phosphorus ions (each with a -3 charge) are required to balance out the charge, ending up with no net charge. Thus, the correct formula would be Ba3P2.