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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.
Thomson in this book 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 noted that no scientist had yet found a positively charged particle smaller than a hydrogen ion.{{sfn|Thomson|1907|pp=23, 26}} He also wrote that the positive charge of an atom is 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> Thomson refused to jump to the conclusion the the basic unit of positive charge has a mass equal to that of the hydrogen ion, arguing that scientists first had to know how many electrons an atom contains.<ref>Thomson (1907), p. 27: "No positively electrified body has yet been found with a mass less than that of a hydrogen atom. We cannot, however, without further investigation infer from this that the mass of the unit of charge of positive electricity is equal to the mass of the hydrogen atom, for all we know about the electrified system is, that the positive electricity is in excess by one unit over the negative electricity; any system containing ''n'' units of positive electricity and (''n''-2) corpuscles would satisfy this condition whatever might be the value of ''n''. Before we can deduce any conclusions as to the mass of the unit of positive electricity we must know something about the number of corpuscles in the system."</ref>
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