- Prout's hypothesis
Prout's hypothesis was an early 19th century attempt to explain the existence of the various
chemical element s through a hypothesis regarding the internal structure of theatom . In 1815 [William Prout (1815). On the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms. "Annals of Philosophy", 6: 321–330. [http://web.lemoyne.edu/~giunta/PROUT.HTML Online reprint] ] and 1816, [William Prout (1816). Correction of a mistake in the essay on the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms. "Annals of Philosophy", 7: 111–13. [http://web.lemoyne.edu/~giunta/PROUT.HTML#prout2 Online reprint] ] the English chemistWilliam Prout published two papers in which he observed that theatomic weight s that had been measured for the elements known at that time appeared to be whole multiples of the atomic weight ofhydrogen . He then hypothesized that the hydrogen atom was the only truly fundamental object, and that the atoms of other elements were actually groupings of various numbers of hydrogen atoms.Influence
Prout's hypothesis remained influential in chemistry throughout the 1820s. However, more careful measurements of the atomic weights, such as those compiled by
Jöns Jakob Berzelius in 1828 orEdward Turner in 1832, "disproved" the hypothesis. In particular the atomic weight ofchlorine , which is 35.45 times that ofhydrogen , could not at the time be explained in terms of Prout's hypothesis. Some came up with thead hoc claim that the basic unit was one-half of a hydrogen atom, but further discrepancies surfaced. This resulted in hypothesis that one-quarter of a hydrogen atom was the common unit. Although these turn out to be wrong, these conjectures catalyzed further measurement of atomic weights, a great benefit to chemistry.The discrepancy in the
atomic weight s was later understood to be the result of multipleisotope s of the same element. Although all elements are the product ofnuclear fusion of hydrogen into higher elements, it is now understood that atoms consist of bothproton s (hydrogen nuclei) andneutron s. Neutrons in nuclei decay into protons by emission ofbeta radiation .The modern version of Prout's rule is that the
atomic mass of a nucleus ofproton number "P" andneutron number "N" is equal to sum of the masses of its constituent protons and neutrons minus itsbinding energy .ee also
*
Whole Number Rule References
Further reading
*
*
*
External links
* [http://www.sjsu.edu/faculty/watkins/semiempirical.htm The Semiempirical Formula for Atomic Masses]
Wikimedia Foundation. 2010.