Some Contributions by Joseph Thomson Are the discovery of the electron, its atomic model, the discovery of isotopes or the cathode ray experiment.
Joseph John Thomson was born in Cheetam Hill, a district of Manchester, England, on December 18, 1856. Also known as"JJ"Thomson, the scientist studied engineering at Owens College, now part of the University of Manchester, and then mathematics In Cambridge.
In 1890 J. J. Thomson married Rose Elizabeth Paget, the daughter of Sir Edward George Paget, with whom I had two children: a girl named Joan Paget Thomson and a boy, George Paget Thomson.
This last one would become a famous scientist, obtaining in 1937, a Nobel Prize to the Physics by its works with electrons.
From a young age, Thomson focused his studies on the structure of atoms, thus discovering the existence of electrons and isotopes, among other contributions.
In 1906, Thomson received the Nobel Prize for Physics,"in recognition of the great merit of his theoretical and experimental research on conducting electricity through gases,"among other awards for his work. (1)
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 age 83, in the City of Cambridge, United Kingdom. The physicist was buried in Westminster Abbey, near the tomb of Sir Isaac Newton. (2)
Thomson's main contributions to science
Discovery of the electron
In 1897, J.J. Thomson discovered a new lighter particle than hydrogen, which was dubbed"electron."
Hydrogen was considered a unit of measurement of 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.
Atomic model of Thomson
The atomic model of Thomson was the structure that the English physicist attributed to the atoms. To the scientist, atoms were a sphere of positive charge.
There, the negatively charged electrons distributed evenly over that positive charge cloud were imbedded, that is, it neutralized the positive charge of the mass of the atom.
This new model replaces that elaborated by Dalton and later will be refuted by Rutherford, disciple of Thomson in the Laboratories Cavendish, of Cambridge.
Separation of atoms
Thomson used positive or anodic rays to separate atoms of different masses. This method allowed him to be able to calculate the electricity transported by each atom and the number of molecules per cubic centimeter.
By being able to divide the atoms of different mass and charge, the physicist discovered the existence of the isotopes. Also in this way, with his study of the positive rays produced a great advance towards mass spectrometry.
Discovery of isotopes
J.J. Thomson discovered that neon ions had different masses, that is, different atomic weight. This is how Thomson demonstrated that neon has two subtypes of isotopes, neon-20 and neon-22.
The isotopes, studied until today, are atoms of the same element but their nuclei have different mass number, since they are composed by different amounts of neutrons in its center.
Cathode ray experiments
Cathode rays are currents of electrons in vacuum tubes, ie glass tubes with two electrodes, one positive and one negative.
When the negative electrode, or also called the cathode, is heated, it emits radiation which is directed towards the positive electrode, or anode, in a straight line if no magnetic field is present in that path.
If the walls of the tube glass are coated with fluorescent material, the impact of the cathodes against that layer produces light projection.
Thomson studied the behavior of cathode rays and arrived at the conclusions that the rays propagated in a straight line.
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 electrons circulating, demonstrating that the electrons had mass.
J.J. Thomson experimented with varying the gas within the cathode ray tube but did not vary the behavior of the electrons. Also, the cathode rays warmed the objects that stood in the path 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 transcendental for the later invention of tube television (CTR) and video cameras.
Mass spectrometer
J.J. Thomson created a first approximation to the Mass spectrometer . This tool allowed the scientist to study the mass / charge ratio of cathode ray tubes and measure how much they deviate by the influence of a magnetic field and the amount of energy they carry.
With this research he concluded that the cathode rays were composed of negatively charged corpuscles, which are inside the atoms, thus postulating the divisibility of the atom and giving rise to the figure of the electron.
Also, the advances in mass spectrometry continued until the present, evolving in different methods to separate the electrons of the atoms.
Thomson was also the first to suggest The first waveguide In 1893. This experiment consisted in propagating electromagnetic waves into a controlled cylindrical cavity, which was first performed in 1897 by Lord Rayleigh, another Nobel Prize in physics.
Waveguides would be widely used in the future, even today with data transmission and fiber optics.
The Legacy of Thomson
The Thomson (Th) was established as mass-load measurement unit in mass spectrometry, proposed by chemists Cooks and Rockwood, in honor of Thomson.
This technique allows to determine the distribution of the molecules of a substance according to its mass and to recognize by this, which are present in a sample of matter.
Thomson (Th) Formula:
Outstanding works
- The Discharge 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
- Nobel Media AB (2014). J. Thomson - Biographical. Nobelprize.org. Nobelprize.org.
- Thomson, Joseph J., Conduction of electricity through gases. Cambridge, University Press, 1903.
- Menchaca Rocha, Arturo. The discreet charm of elemental particles.
- Christen, Hans Rudolf, Foundations of General and Inorganic Chemistry, Volume 1 . Barcelona, Spain. Ediciones Reverté S.A., 1986.
- Arzani, Aurora Cortina, General Elemental Chemistry. Mexico, Porrúa Publishing House, 1967.
- R. G. Cooks, A. L. Rockwood. Rapid Commun. Mass Spectrom . 5, 93 (1991).