Final answer:
The chemical formula for trisilicon dibromide is Si3Br2, using the prefixes 'tri-' and 'di-' to indicate the presence of three silicon atoms and two bromine atoms.
Step-by-step explanation:
To write the chemical formula for the molecular compound trisilicon dibromide, we must look at the prefixes given in the name. The prefix 'tri-' means three, indicating the presence of three silicon atoms. The prefix 'di-' means two, indicating the presence of two bromine atoms. Therefore, using these numerical prefixes, the formula for trisilicon dibromide is Si3Br2, which corresponds to option A. This method of determining formulas from compound names is common for molecular compounds, where prefixes like 'mono-', 'di-', 'tri-', 'tetra-', and so on, indicate the number of atoms of each element present in the compound.