To determine the correct chemical formula for the compound formed when beryllium (Be) and fluorine (F) combine, we need to consider their valences.
Beryllium (Be) has a valence of +2 because it tends to lose its two electrons. Fluorine (F) has a valence of -1 because it tends to gain one electron.
When combining these two elements, the charges must balance. Since beryllium has a +2 charge and each fluorine has a -1 charge, two fluorine atoms will be needed to balance the +2 charge from one beryllium atom.
Thus, the correct formula for the product of the reaction would be BeF₂.
So, the answer is B. BeF₂.