What is the formula of the compound being formed here by the process of ionic bonding?
The answer is calcium bromide, `CaBr_2` . Calcium has 2 valence electrons, as seen from the electron dot formula. It readily donates them to achieve stable electronic configuration and forms the cation Ca(II) or `Ca^(2+)` . Bromine, on the other hand, is a halide and has 7 valence electrons, i.e. it is one electron short of stable electronic configuration. Bromine, being more electronegative as compared to calcium, readily accepts electrons from calcium (or other metals), to achieve 8 electrons in outermost orbital. Here we can see that calcium is donating its two valence electrons, one each to each bromine atom. This way all the atoms (one calcium and 2 bromine atoms) will achieve stable configuration and we will obtain the ionic compound, CaBr2.
Hope this helps.