4. Choose one of the compounds from the table and explain how you know the numbers of atoms in your formula. I chose Hydrogen Chloride. The chemical formula is HCI.

Chemical formulas are written with subscripts or little numbers at the bottom. If there are no numbers, it's one, as we don't write one. In HCl there is one hydrogen atom and one chlorine atom chemically bonded to form a covalent molecular compound of hydrochloride acid.