What did Robert Millikan discover about the electron through his oil drop experiment?

• A. The energy levels of electrons in atoms
• B. The mass of the electron
• C. The exact charge of a single electron
• D. The existence of the neutron

Answer: (C)

Verified step by step guidance

1. Understand the context of Millikan's oil drop experiment, which was designed to measure a fundamental property of the electron by observing tiny charged oil droplets suspended in an electric field.
2. Recognize that Millikan's experiment allowed him to determine the charge on each oil droplet by balancing gravitational and electric forces, enabling precise measurement of the electron's charge.
3. Note that by analyzing multiple droplets, Millikan found that the charges were always multiples of a smallest, consistent value, which he identified as the charge of a single electron.
4. Understand that this discovery was crucial because it provided the first accurate measurement of the elementary electric charge, a fundamental constant in physics and chemistry.
5. Clarify that Millikan's experiment did not measure the electron's mass directly, nor did it address energy levels in atoms or the existence of neutrons; its key contribution was determining the exact charge of the electron.