Here's why:

* Be represents the element beryllium.

* Br represents the element bromine.

* 2 indicates that there are two bromine atoms for every beryllium atom.

Since beryllium is in group 2 of the periodic table, it forms a +2 cation (Be²⁺), and bromine is in group 17, forming a -1 anion (Br⁻). The charges balance out to form the neutral compound BeBr2.