What is the chemical formula for magnesium bromide?

The atoms in any molecule are represented by their corresponding amounts in a chemical formula. Since a chemical formula identifies the precise molecules, it is often referred to as the molecule's molecular formula. The cation is put first in a chemical formula, followed by the anion.

Any substance's chemical formula gives the precise numbers of atoms that make up that compound. Any molecule's cation is identified and written before its anion when formulating the chemical formula for that molecule. The ion carrying the positive charge while accepting electrons is called a cation, whereas the ion carrying the negative charge while accepting electrons is called an anion.

The given compound Magnesium Bromide contains Magnesium and Bromine as two atoms. Since, we know that while naming a chemical compound, the cation is named and written first followed by the anion.

So, here as the name suggests Magnesium is written first so its cation is ${\mathrm{Mg}}^{2+}$ and Bromine is written after so ${\mathrm{Br}}^{-}$ is the anion.

We see that, magnesium has 2 valence electrons so it has 2 positive charges whereas, bromine has 1 valence electron and has 1 negative charge.

Now to balance the charges, Bromine will have to be given 2 charges from Magnesium.

So, the chemical formula for Magnesium Bromide will be ${\mathrm{MgBr}}_2$.

Hence, option B is correct.