Final answer:
In modern chemistry, the atom or molecule that donates electrons is called a nucleophile.
Step-by-step explanation:
In modern chemistry, the atom or molecule that donates electrons, such as magnesium, is called a nucleophile. Nucleophiles are electron-rich species that seek electron-deficient atoms or molecules to form bonds with. In the case of magnesium, it donates two electrons to oxygen to form an ionic bond and create MgO.