How were the protons discovered?

Answer 1

The atomic nucleus was discovered by Ernest Rutherford in 1911. In 1913, it was proven that the charge of the nucleus was equal to its atomic number. In 1919, Rutherford proved that the nuclei of all atoms contained particles described as hydrogen nuclei, and this is considered the discovery of the proton.

Answer 2

In the mid-nineteenth century, Julius Plücker investigated the light emitted in discharge tubes and the influence of magnetic fields on the glow. Later, in 1869, Johann Wilhelm Hittorf studied discharge tubes with energy rays extending from a negative electrode, the cathode. These rays produced a fluorescence when they hit a tube's glass walls, and when interrupted by a solid object they cast a shadow.

By the 1870s Goldstein had undertaken his own investigations of discharge tubes, and named the light emissions studied by others kathodenstrahlen, or cathode rays. In 1886, he discovered that discharge tubes with a perforated cathode also emit a glow at the cathode end. Goldstein concluded that in addition to the already-known cathode rays, later recognized as electrons moving from the negatively-charged cathode toward the positively-charged anode, there is another ray that travels in the opposite direction. Because these latter rays passed through the holes, or channels, in the cathode, Goldstein called them kanalstrahlen, or canal rays. They are composed of positive ions whose identity depends on the residual gas inside the tube. It was another of Helmholtz's students, Wilhelm Wien, who later conducted extensive studies of canal rays, and in time this work would become part of the basis for mass spectrometry.

The anode ray with the smallest e/m ratio comes from hydrogen gas (H2), and is made of H+ ions. In other words this ray is made of protons. Goldstein's work with anode rays of H+ was apparently the first observation of the proton, although strictly speaking it might be argued that it was Wien who measured the e/m ratio of the proton and should be credited with its discovery.

Goldstein also used discharge tubes to investigate comets. An object, such as a small ball of glass or iron, placed in the path of cathode rays produces secondary emissions to the sides, flaring outwards in a manner reminiscent of a comet's tail. See the work of Hedenus for pictures and additional information.[2]

Answer 3

Ludwig Eduard Boltzmann made a significant contribution in terms of advocating for the atomic model. Boltzmann's story is some ways a parallel to that of Ignaz Semmelweis on iatrogenic effects in hospital settings. Both were ridiculed and committed suicide before being vindicated.

See also: Sigmund Freud and the neuron as the "atom" of neuroanatomy.

Boltzmann in particular challenged the notion that particles were merely convenient notions to which nothing real corresponded.

Compare Feynman diagrams as a notation which can itself be viewed as a "theory".

Answer 4

Ernest Rutherford