Two atoms with an electronegativity difference of 0.4 form a bond that is
1. ionic, because electrons are shared
2. ionic, because electrons are transferred
3. covalent, because electrons are shared
4. covalent, because electrons are transferred

The correct answer is 3.

Explanation:

Ionic bond is defined as the bond formed when there is complete transfer of electrons from one atom to another atom. Example: NaCl

Covalent bond is defined as the bond formed when there is sharing of electrons between two atoms. The atom which takes the shared pair of electron towards itself is known as electronegative atom. Example: HCl

Dependency of electronegativity difference on ionic and covalent polar bond:

If the electronegativity difference is greater than 0 and less than 2.0, then the bond is covalent polar in nature and it shares the electrons.

And if the electronegativity difference is 2.0 or greater, then the bond is ionic polar in nature and the electrons are transferred from one atom to another.

As, the electronegativity difference given is 0.4, so the bond will be covalent and sharing of electrons will be there.