What happens when magnesium reacts with fluorine?
a. electrons are shared between the magnesium atoms and the fluorine atoms.
b. electrons move from the magnesium atoms to the fluorine atoms.
c. electrons become delocalized among the atoms.
d. electrons move from the fluorine atoms to the magnesium atoms.

B.Electrons move from the magnesium atoms to the fluorine atoms.

Explanation:

A covalent bond is formed when an element shares its valence electron with another element. This bond is formed between two non metals.

An ionic bond is formed when an element completely transfers its valence electron to another element. The element which donates the electron is known as electropositive element and the element which accepts the electrons is known as electronegative element. This bond is formed between a metal and an non-metal.

Electronic configuration of magnesium:

Magnesium atom will loose two electrons to gain noble gas configuration and form sodium cation with +2 charge.

Electronic configuration of flourine:

Flourine atom will gain one electron to gain noble gas configuration and form flouride ion with -1 charge.

When magnesium reacts with flourine, two electrons from magnesium are transferred to two atoms of fluorine.