2. Which bond is polar covalent?

a) H2
b) Cl2
c) HCl
d) O2

And HCl it is. Note that the bonds between O2, H2, Cl2 are between the SAME atoms; therefore, there is NO difference in electronegativity and they are 100% covalent (except it is argued by some that we can write resonance structures that contain charges and that contributes to a tiny, tiny amount of polarity but it is essentially zero (if it exists).

Which bond is between unlike atoms?

To determine which bond is polar covalent among the given options, we need to understand the concept of electronegativity.

Electronegativity is a measure of an atom's ability to attract the shared electrons in a covalent bond. When two atoms with different electronegativities form a covalent bond, the shared electrons tend to be pulled closer to the more electronegative atom, resulting in a polar covalent bond.

Let's determine the electronegativity of the elements involved in each option:

a) H2: Hydrogen (H) has an electronegativity value of approximately 2.2. Since both hydrogen atoms have the same electronegativity, the bond is nonpolar covalent.

b) Cl2: Chlorine (Cl) has an electronegativity value of approximately 3.2. Since both chlorine atoms have the same electronegativity, the bond is nonpolar covalent.

c) HCl: Hydrogen (H) has an electronegativity value of approximately 2.2, while chlorine (Cl) has an electronegativity of approximately 3.2. As there is a difference in electronegativity between the two atoms, the bond is polar covalent.

d) O2: Oxygen (O) has an electronegativity value of approximately 3.5. Since both oxygen atoms have the same electronegativity, the bond is nonpolar covalent.

Therefore, among the given options, the bond that is polar covalent is c) HCl.

HCL ?