Prout's hypothesis

Prout's hypothesis was an early 19th-century attempt to explain the existence of the various <a href="/facts/Chemical_element/0jducgWD">chemical elements</a> through a hypothesis regarding the internal structure of the <a href="/facts/Atom/69syB8dH">atom</a>. In 1815 and 1816, the <a href="/facts/England/U9mE5bGL">English</a> chemist <a href="/facts/William_Prout/JT6mhP0M">William Prout</a> published two papers in which he observed that the <a href="/facts/Atomic_weight/A3vbuz2n">atomic weights</a> that had been measured for the elements known at that time appeared to be whole multiples of the atomic weight of <a href="/facts/Hydrogen/BoYHjl0J">hydrogen</a>. He then hypothesized that the hydrogen atom was the only truly fundamental object, which he called protyle, and that the atoms of other elements were actually groupings of various numbers of hydrogen atoms.
Prout's hypothesis was an influence on <a href="/facts/Ernest_Rutherford/hjjMEskl">Ernest Rutherford</a> when he succeeded in "knocking" hydrogen nuclei out of nitrogen atoms with alpha particles in 1917, and thus concluded that perhaps the nuclei of all elements were made of such particles (the hydrogen nucleus), which in 1920 he suggested be named <a href="/facts/Proton/clCjepXP">protons</a>, from the suffix "-on" for particles, added to the stem of Prout's word "protyle". The assumption as discussed by Rutherford was of a <a href="/facts/Nucleus_(atomic_structure)/orpIm5Xl">nucleus</a> consisting of Z + N = A <a href="/facts/Proton/clCjepXP">protons</a> plus N <a href="/facts/Electron/L0KBo5cW">electrons</a> somehow trapped within thereby reducing the positive charge to +Z as observed and vaguely explaining <a href="/facts/Beta_decay/vxTBlckp">beta decay</a> <a href="/facts/Radioactive_decay/Ya6FVjt4">radioactivity</a>. Such a nuclear constitution was known to be inconsistent with dynamics either <a href="/facts/Classical_physics/gGnINVPE">classical</a> or early <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum</a> but seemed inevitable until the <a href="/facts/Neutron/oRCM1geb">neutron</a> hypothesis by Rutherford and discovery by English physicist <a href="/facts/James_Chadwick/nwStNAzI">James Chadwick</a>.
The discrepancy between Prout's hypothesis and the known variation of some atomic weights to values far from integral multiples of hydrogen, was explained between 1913 and 1932 by the discovery of <a href="/facts/Isotope/KD9B1y6o">isotopes</a> and the <a href="/facts/Neutron/oRCM1geb">neutron</a>. According to the <a href="/facts/Whole_number_rule/VWvM5bpK">whole number rule</a> of <a href="/facts/Francis_Aston/DVoj9ebB">Francis Aston</a>, Prout's hypothesis is correct for <a href="/facts/Atomic_mass/J1FJY9MV">atomic masses</a> of individual isotopes, with an error of at most 1%.

Prout's hypothesis open-in-new

Prout's hypothesis