Final answer:
The neutral atom Cl gains 1 electron to become the chloride ion, forming an ionic bond with the barium cation in BaCl², resulting in an overall neutral compound.
Step-by-step explanation:
The statement that best explains why BaCl² is an ionic compound is:
d. The neutral atom Cl gains 1 electron.
In an ionic compound, one atom loses electrons to become a cation (positively charged ion), while another atom gains those electrons to become an anion (negatively charged ion). In the case of BaCl², the neutral chlorine atom gains one electron to become chloride ion (Cl-) with a net charge of -1. This allows it to form an ionic bond with the barium cation (Ba²+) which has a net charge of +2, resulting in an overall neutral compound, BaCl².