Which factor is primarily responsible for the positive charge at one end of a molecule, resulting in a dipole moment?

• A. The molecular mass of the atoms involved
• B. The presence of resonance structures
• C. A difference in electronegativity between atoms in a bond
• D. Equal sharing of electrons between atoms

Answer: (C)

Verified step by step guidance

1. Understand that a dipole moment in a molecule arises when there is an uneven distribution of electron density between atoms bonded together.
2. Recall that electronegativity is a measure of an atom's ability to attract shared electrons in a chemical bond.
3. Recognize that when two atoms in a bond have different electronegativities, the electrons are pulled more toward the more electronegative atom, creating a partial negative charge there and a partial positive charge on the other atom.
4. Note that this separation of charge creates a dipole moment, with one end of the molecule being partially positive and the other partially negative.
5. Conclude that the primary factor responsible for the positive charge at one end of a molecule, resulting in a dipole moment, is the difference in electronegativity between the atoms in the bond.