What are the chemical formula and common names for these compounds?

SiBr4 is silicon tetrabromide. HI is hydrogen iodide or can be called hydroiodic acid. P + Br2 -> PBr3 is called phosphorous tribromide. I am not aware of P and Br made to combine to form P2Br3. Anyway, These are involving two elements each. The more metallic is named first with its simple element name. Then this is followed with the more nonmetallic element with -ide added. Depending on how many atoms of the element in the molecule, tri for three, tetra for four, penta for 5, etc., a prefix is added to the nonmetal's name. AND what that number is depends on the oxidation numbers of the elements used. Which brings me to tell you to get to know the periodic chart. A good one will show the oxidation numbers for all the elements.

Misread: I saw SiBr4 and thought SnBr4: Tin(IV) bromide or stannic bromide Silicon tetrabromide Hydrogen iodide or (in aqueous solution) hydroiodic acid Phosphorous tribromide You don't use phosphorous(III) bromide because that notation is for metals, and phosphorous is not a metal. There is also a phosphorous pentabromide.

Misread: I saw SiBr4 and thought SnBr4: Tin(IV) bromide or stannic bromide Silicon tetrabromide Hydrogen iodide or (in aqueous solution) hydroiodic acid Phosphorous tribromide You don't use phosphorous(III) bromide because that notation is for metals, and phosphorous is not a metal. There is also a phosphorous pentabromide.

Silicon Bromate Hydrogen Iodide (Or Iodidic Acid) Diphosphorous tribromide

Silicon Bromate Hydrogen Iodide (Or Iodidic Acid) Diphosphorous tribromide