Plum pudding model: Difference between revisions

Revision as of 18:56, 22 October 2024

Revision as of 20:39, 23 October 2024

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In Chapter 6, he further elaborates his experiment using magnetised pins in water, providing an expanded table. For instance, if 59 pins were placed in the pool, they would arrange themselves in concentric rings of the order 20-16-13-8-2 (from outermost to innermost).

In Chapter 7, Thomson summarised his 1906 results on the number of electrons in an atom. He included one important correction: he replaced the beta-particle analysis with one based on the cathode ray experiments of [[August Becker]], giving a result in better agreement with other approaches to the problem.<ref name=Heilbron1968/>{{rp|273}} Experiments by other scientists in this field had shown that atoms contain far fewer electrons than Thomson previously thought. Thomson now believed the number of electrons in an atom was a small multiple of its atomic weight: "the number of corpuscles in an atom of any element is proportional to the atomic weight of the element — it is a multiple, and not a large one, of the atomic weight of the element."<ref>{{harvnb|Thomson|1907|p=27}}</ref> This meant that almost all of the atom's mass had to be carried by the positive sphere, whatever it was made of.

ThisThomson meantin that almost all of the atom's mass had to be carried by the positive sphere, whatever it was made of.this Hebook estimated that a hydrogen atom is 1,700 times heavier than an electron ([[Proton-to-electron mass ratio|the current measurement is 1,837]]).<ref>{{harvnb|Thomson|1907|p=162}}: "Since the mass of a corpuscle is only about one-seventeen-hundredth part of that of an atom of hydrogen, it follows that if there are only a few corpuscles in the hydrogen atom the mass of the atom must in the main be due to its other constituent — the positive electricity."</ref> Thomson notesnoted that no scientist had yet found a positively charged particle smaller than a hydrogen ion.{{sfn|Thomson|1907|pp=23, 26}} He also says that the positive charge of an atom was a multiple of a basic unit of positive charge, equal to the negative charge of an electron.<ref>J. J. Thomson (1907). ''The Corpuscular Theory of Matter''. p. 26-27: "In an unelectrified atom there are as many units of positive electricity as there are of negative; an atom with a unit of positive charge is a neutral atom which has lost one corpuscle, while an atom with a unit of negative charge is a neutral atom to which an additional corpuscle has been attached."</ref>

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