Magnesium bromide (MgBr2) is an ionic compound. This means that it is composed of positively and negatively charged ions. In the case of MgBr2, the magnesium atom loses two electrons to become a positively charged magnesium ion (Mg2+). The bromine atoms each gain one electron to become negatively charged bromide ions (Br-). The electrostatic attraction between the magnesium ions and the bromide ions holds the compound together.