Which key information about electrons was determined by Millikan's oil drop experiment?

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

Answer: (D)

Verified step by step guidance

1. Understand the purpose of Millikan's oil drop experiment, which was designed to measure the charge of a single electron by observing tiny charged oil droplets suspended in an electric field.
2. Recognize that Millikan balanced the gravitational force on the oil droplets with the electric force, allowing him to calculate the charge on each droplet using the equation \(qE = mg\), where \(q\) is the charge, \(E\) is the electric field strength, \(m\) is the mass of the droplet, and \(g\) is the acceleration due to gravity.
3. Note that by measuring the charges on many droplets, Millikan found that the charges were always multiples of a smallest value, which he identified as the fundamental charge of a single electron.
4. Understand that this experiment did not determine the mass of a proton, the discovery of the neutron, or the energy levels of electrons in atoms, but specifically the quantized charge of the electron.
5. Conclude that the key information determined by Millikan's oil drop experiment is the charge of a single electron.