Which molecule has the most or the least polar binding: NaI, LiBr, Cl2, KCl?
The correct answer and explanation is:
Correct Answer:
Most polar binding: KCl
Least polar binding: Cl₂
Explanation:
Polarity of a bond depends on the difference in electronegativity between the atoms involved. A greater difference results in a more polar bond, and a smaller or zero difference results in a less polar or non-polar bond.
Most Polar: KCl (Potassium Chloride)
KCl has the most polar bond among the given molecules. Potassium (K) is a metal with very low electronegativity, and chlorine (Cl) is a nonmetal with high electronegativity. The electronegativity difference between K (0.82) and Cl (3.16) is about 2.34. This large difference causes a significant transfer of electrons from K to Cl, making the bond highly ionic and polar. K loses one electron to become K⁺, and Cl gains one to become Cl⁻. This electron transfer forms a strong electrostatic attraction, characteristic of a polar ionic bond.
Least Polar: Cl₂ (Chlorine molecule)
Cl₂ is a diatomic molecule made of two identical chlorine atoms. Since both atoms have the same electronegativity (3.16), the electron pair in the bond is shared equally. This results in a nonpolar covalent bond, where there is no separation of charge across the molecule. Therefore, Cl₂ has the least polar or zero polarity among the options.
Other Molecules:
NaI (Sodium Iodide) and LiBr (Lithium Bromide) are also ionic compounds like KCl, but their electronegativity differences are slightly smaller. Na (0.93) and I (2.66) differ by 1.73, while Li (0.98) and Br (2.96) differ by 1.98. These values are less than the K–Cl difference, so their bonds are slightly less polar than KCl, but more polar than covalent Cl₂.
Thus, KCl has the most polar bond, and Cl₂ has the least polar bond.