* Electrostatic Attraction: Magnesium (Mg) is a metal and bromine (Br) is a nonmetal. Metals tend to lose electrons, forming positive ions (cations), while nonmetals tend to gain electrons, forming negative ions (anions). In MgBr₂, magnesium loses two electrons to become Mg²⁺, and each bromine atom gains one electron to become Br⁻. The strong electrostatic attraction between these oppositely charged ions is what forms the ionic bond.

* Electronegativity Difference: The electronegativity difference between magnesium and bromine is large enough (2.9 for Br and 1.3 for Mg) to classify the bond as ionic. A difference of 1.7 or greater is generally considered to indicate an ionic bond.

Key takeaway: Ionic compounds are formed between metals and nonmetals, resulting in a transfer of electrons and strong electrostatic attraction between the ions.