A Level Chemistry OCR Practice Exam

Which factor primarily influences the electronegativity difference in a polar covalent bond?

1. Atomic number of the molecules involved

2. Atomic mass of the molecules involved

3. Atomic radius of the elements involved

4. Ionization energy of the elements involved

The correct answer is: Atomic number of the molecules involved

The most relevant factor influencing the electronegativity difference in a polar covalent bond is the atomic number of the elements involved. Electronegativity is a measure of the ability of an atom to attract shared electrons in a chemical bond. Generally, as the atomic number increases within a group, the electronegativity can also increase due to the greater positive charge in the nucleus, which enhances the attraction for electrons. While the atomic mass, atomic radius, and ionization energy can play roles in the overall behavior of elements, they are not direct measures of electronegativity. Atomic mass may influence molecular weight and bonding characteristics but does not account for the ability to attract electrons. The atomic radius, although it can affect the distance between nuclei in a bond, is secondary to the effective nuclear charge that the atomic number influences. Ionization energy relates to the energy required to remove an electron, which can affect reactivity and bond formation but does not directly dictate the polar nature of covalent bonds. Thus, the atomic number is the primary influence when considering the electronegativity difference in polar covalent bonds.