JOSEPH THOMSON: BIOGRAPHY AND CONTRIBUTIONS TO SCIENCE AND CHEMISTRY - CHEMISTRY - 2025

Joseph John Thomson was an outstanding chemist for various contributions, such as the discovery of the electron, its atomic model, the discovery of isotopes or the cathode ray experiment.

He was born in Cheetam Hill, a district of Manchester, England, on December 18, 1856. Also known as “JJ” Thomson, he studied engineering at Owens College, now part of the University of Manchester, and later mathematics at Cambridge.

In 1890, JJ Thomson married Rose Elizabeth Paget, daughter of the physician Sir Edward George Paget, with whom he had two children: a girl, named Joan Paget Thomson, and a boy, George Paget Thomson.

The latter would become a famous scientist, obtaining in 1937, a Nobel Prize in Physics for his work with electrons.

From a young age, Thomson focused his studies on the structure of atoms, thus discovering the existence of electrons and isotopes, among many of his contributions.

In 1906, Thomson received the Nobel Prize in Physics, "in recognition of the great merit of his theoretical and experimental research on the conduction of electricity through gases", among many other awards for his work. (one)

In 1908, he was knighted by the British crown and served as Honorary Professor of Physics at Cambridge and at the Royal Institute, London.

He died on August 30, 1940, at the age of 83, in the City of Cambridge, United Kingdom. The physicist was buried in Westminster Abbey, near the grave of Sir Isaac Newton. (two)

Thomson's main contributions to science

Discovery of the electron

In 1897, JJ Thomson discovered a new particle lighter than hydrogen, which was named "electron."

Hydrogen was considered a unit of measurement for atomic weight. Until that moment, the atom was the smallest division of matter.

In this sense, Thomson was the first to discover negatively charged corpuscular subatomic particles.

Thomson's atomic model

Thomson's atomic model was the structure that the English physicist attributed to atoms. For the scientist, atoms were a sphere of positive charge.

There the electrons of negative charge distributed uniformly on that cloud of positive charge were embedded, that is to say, that neutralizes the positive charge of the mass of the atom.

This new model replaces the one developed by Dalton and will later be refuted by Rutherford, a disciple of Thomson at Cavendish Laboratories, Cambridge.

Atom separation

Thomson used positive or anodic rays to separate atoms of different masses. This method enabled him to calculate the electricity carried by each atom and the number of molecules per cubic centimeter.

By being able to divide atoms of different mass and charge, the physicist discovered the existence of isotopes. Also in this way, with his study of positive rays, he produced a great advance towards mass spectrometry.

Discovery of isotopes

JJ Thomson discovered that neon ions had different masses, that is, different atomic weights. This is how Thomson showed that neon has two subtypes of isotopes, neon-20 and neon-22.

The isotopes, studied to this day, are atoms of the same element but their nuclei have different mass numbers, since they are composed of different amounts of neutrons in their center.

Cathode ray experiments

Cathode rays are streams of electrons in vacuum tubes, that is, glass tubes with two electrodes, one positive and one negative.

When the negative electrode, or also called the cathode, is heated, it emits radiation that is directed towards the positive electrode, or anode, in a straight line if no magnetic field is present in that path.

If the glass walls of the tube are covered with fluorescent material, the hit of the cathodes against that layer produces the projection of light.

Thomson studied the behavior of cathode rays and came to the conclusions that the rays traveled in straight lines.

Also that these rays could be diverted from their path by the presence of a magnet, that is, a magnetic field. In addition, the rays could move the blades with the force of the mass of the circulating electrons, thus demonstrating that the electrons had mass.

JJ Thomson experimented with varying the gas inside the cathode ray tube but did not vary the behavior of the electrons. Also, cathode rays heated objects that got in the way between electrodes.

In conclusion, Thomson had shown that cathode rays had light, mechanical, chemical and thermal effects.

Cathode ray tubes and their light properties were crucial for the later invention of tube television (CTR) and video cameras.

Mass spectrometer

JJ Thomson created a first approach to the mass spectrometer. This tool allowed the scientist to study the mass / charge ratio of cathode ray tubes, and to measure how much they are deflected by the influence of a magnetic field and the amount of energy they carry.

With this research he came to the conclusion that cathode rays were composed of negatively charged corpuscles, which are inside atoms, thus postulating the divisibility of the atom and giving rise to the figure of the electron.

Also, advances in mass spectrometry continued to the present day, evolving into different methods to separate electrons from atoms.

In addition, Thomson was the first to suggest the first waveguide in 1893. This experiment consisted of propagating electromagnetic waves within a controlled cylindrical cavity, which was first performed in 1897 by Lord Rayleigh, another Nobel Prize winner in Physics.

Waveguides would be widely used in the future, even today with data transmission and fiber optics.

Thomson's legacy

The Thomson (Th) was established as a mass-charge unit of measurement in mass spectrometry, proposed by the chemists Cooks and Rockwood, in honor of Thomson.

This technique allows to determine the distribution of the molecules of a substance according to their mass and, to recognize by this, which ones are present in a sample of matter.

Thomson's formula (Th):

Outstanding works

• The Discarge of Electricity Through Gases, Conduction of Electricity Through Gases (1900).
• The Corpuscular Theory of Matter, The Electron in Chemistry and Recollections and Reflections (1907).
• Beyond the Electron (1928).

References

1. Nobel Media AB (2014). J. Thomson - Biographical. Nobelprize.org. nobelprize.org.
2. Thomson, Joseph J., Conduction of electricity through gases. Cambridge, University Press, 1903.
3. Menchaca Rocha, Arturo. The discreet charm of elementary particles.
4. Christen, Hans Rudolf, Fundamentals of General and Inorganic Chemistry, Volume 1. Barcelona, ​​Spain. Ediciones Reverté SA, 1986.
5. Arzani, Aurora Cortina, General Elemental Chemistry. Mexico, Editorial Porrúa, 1967.
6. RG Cooks, AL Rockwood. Rapid Commun. Mass Spectrom. 5, 93 (1991).