Which of the following -s an ionic compound? Cl2 CO2 HCN MgCl2

The correct answer is $$MgCl2$$ .

Ionic compounds are formed when a metal atom donates one or more electrons to a non-metal atom, resulting in the formation of positively charged metal ions and negatively charged non-metal ions. These ions are held together by strong electrostatic forces of attraction.

In the given options, $$Cl2$$ is a diatomic molecule composed of two chlorine atoms, $$CO2$$ is a covalent compound formed by the sharing of electrons between carbon and oxygen atoms, and HCN is a covalent compound formed by the sharing of electrons between hydrogen, carbon, and nitrogen atoms.

On the other hand, $$MgCl2$$ is an ionic compound formed by the transfer of electrons from magnesium (a metal) to chlorine (a non-metal). In this compound, magnesium loses two electrons to form a $$Mg^{2+}$$ ion, while chlorine gains one electron to form two $$Cl^{-}$$ ions. The resulting ionic compound is $$MgCl2$$ , where the positive and negative ions are held together by strong electrostatic forces of attraction.