Chemistry 2001 JAMB Past Questions - Question 8: Millikan's contribution to the development of atomic theory is the determination of

Correct Answer

A

Explanation

Robert A. Millikan made significant contributions to the development of atomic theory through his famous oil-drop experiment. In the early 20th century, there was still uncertainty about the nature of atoms and their fundamental properties. One key question was the precise charge of an electron.

Millikan's experiment, conducted between 1909 and 1913, involved measuring the charge of individual electrons. He sprayed tiny oil droplets into a chamber and then observed their motion between two charged plates. By carefully adjusting the electric field in the chamber, Millikan could determine the smallest unit of electric charge.

The key findings from Millikan's experiment were:

1. **Quantization of Electric Charge:** Millikan's work provided experimental confirmation that the electric charge on an individual electron is quantized, meaning it comes in discrete, specific units.

2. **Charge of an Electron:** He determined the charge of a single electron to be approximately \(1.5924 \times 10^{-19}\) coulombs.

3. **Mass of an Electron:** By combining his results with other measurements, such as the charge-to-mass ratio of electrons measured by J.J. Thomson, Millikan also made an indirect determination of the mass of an electron.

Millikan's precise measurements of the charge of the electron played a crucial role in the development of atomic theory, providing experimental evidence that supported the idea of discrete, indivisible particles with specific properties. His work contributed to the overall understanding of the structure of atoms and the fundamental particles that constitute them.