The ratio of metal cationic (+) atom to nonmetal anionic (-) atom in the compound is 1:2.
The term electron configuration shows the arrangement of electrons in an atom. We have the configurations of the atoms as follows;
magnesium - 1s22s22p63s2
bromine - 1s22s22p63s23p64s23d104p5
We can see that the catio is Mg^2+ and the anioin is Br^- hence the ratio of metal cationic (+) atom to nonmetal anionic (-) atom in the compound is 1:2.
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