A classmate of yours is convinced that he knows everything about electronegativity. (a) In the case of atoms X and Y having different electronegativities, he says, the diatomic molecule X–Y must be polar. Is your classmate correct? (b) Your classmate says that the farther the two atoms are apart in a bond, the larger the dipole moment will be. Is your classmate correct?

Verified step by step guidance

1. Step 1: Understand the concept of electronegativity. Electronegativity is the ability of an atom to attract shared electrons in a chemical bond. It varies across the periodic table, generally increasing from left to right and decreasing from top to bottom.
2. Step 2: Analyze part (a) of the problem. When two atoms, X and Y, have different electronegativities, the electrons in the bond are not shared equally, leading to a polar bond. However, the overall polarity of the molecule depends on its geometry. If the molecule is symmetrical, it might still be nonpolar despite having polar bonds.
3. Step 3: Consider part (b) of the problem. The dipole moment is a measure of the separation of positive and negative charges in a molecule. It depends on both the difference in electronegativity and the distance between the charges. However, the statement that the farther apart the atoms are, the larger the dipole moment, is not entirely correct. The dipole moment is also influenced by the magnitude of the charge difference.
4. Step 4: Clarify the relationship between bond length and dipole moment. While a longer bond length can contribute to a larger dipole moment, it is not the sole factor. The difference in electronegativity is crucial in determining the dipole moment.
5. Step 5: Summarize the findings. For part (a), a molecule with atoms of different electronegativities can be polar, but molecular geometry must be considered. For part (b), the dipole moment is influenced by both the electronegativity difference and the bond length, not just the distance between atoms.