Question

What leads to the establishment of the particle nature of electron?

Short answer

Answer: The key experiments and discoveries that led to the establishment of the particle nature of electrons include J.J. Thomson's cathode ray experiments and determination of the charge-to-mass ratio of electrons, Robert Millikan's oil drop experiment, and Ernest Rutherford's gold foil experiment. These experiments demonstrated that electrons are discrete, negatively charged subatomic particles with particle-like properties.

Step-by-step solution

1. Discovery of Electrons

In 1897, British physicist J.J. Thomson conducted a series of experiments called cathode ray experiments, in which he passed an electrical current through a sealed glass tube filled with low-pressure gas. He observed that as the electrical current passed through the tube, a beam of negatively charged particles, which he called "corpuscles," was emitted. These particles were later named electrons. Thomson's experiment demonstrated that electrons are negatively charged subatomic particles, thus showing that they have particle-like properties.

2. Charge-to-Mass Ratio of Electrons

In his cathode ray experiments, J.J. Thomson also determined the charge-to-mass ratio of electrons. He used magnetic fields to deflect the trajectory of the cathode rays (electrons) and measured the extent of deflection. By comparing their deflection to that of other known charged particles, he deduced the charge-to-mass ratio. The fact that these particles had a definite mass and charge further confirmed their particle-like nature.

3. Millikan's Oil Drop Experiment

In 1909, American physicist Robert Millikan performed the famous oil drop experiment, which provided more evidence supporting the particle nature of electrons. Millikan carefully balanced the forces of gravity and electric fields on tiny oil droplets, allowing them to hover in mid-air. By measuring the charge on these droplets, he was able to determine the elementary charge of an electron. This experiment provided further evidence of the discrete, particle-like nature of electrons.

4. Rutherford's Gold Foil Experiment

In 1911, Ernest Rutherford conducted the gold foil experiment, which facilitated a better understanding of the structure of atoms. He directed a beam of alpha particles at a thin gold foil and observed their scattering patterns on a fluorescent screen. Most of the alpha particles passed straight through the foil, but some were deflected at large angles, indicating the presence of a dense, positively charged core (later named the nucleus) at the center of the atom. This experiment showed that electrons occupy the space surrounding the nucleus as discrete particles. In conclusion, the establishment of the particle nature of electrons is a result of several significant experiments and discoveries, including the discovery of electrons by J.J. Thomson, the determination of the charge-to-mass ratio of electrons, Millikan's oil drop experiment, and Rutherford's gold foil experiment. These experiments collectively demonstrated that electrons are discrete, negatively charged subatomic particles.