Henry Moseley

(History of the Atomic Theory) - by Brason Jones

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Photo of Henry Moseley (November 23, 1887-August 10, 1915)

Henry Moseley was responsible for proving the hypothesis of Antonius van den Broek to be correct and restructuring the periodic table. This hypothesis suggested that the atomic numbers of elements on the periodic table could be equal to the charge of an atom's nucleus.
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Though not living up to his own academic expectations while attending the University of Oxford, Moseley began to study with Ernest Rutherford at the University of Manchester. While researching with Rutherford, Moseley additionally taught physics; after a year at Manchester, he was offered a research fellowship by Rutherford. Thus he was allowed to eliminate his duties of teaching and focus solely on scientific discovery.
After roughly a year of receiving his fellowship at Manchester, Moseley moved back to Oxford. Here he used his knowledge of electrons and X-rays to attempt to learn what occurs within atoms. Moseley began to record data of an experiment that involved shooting electrons at different chemical elements, which in turn would create X-rays, and discovered that the frequencies of the X-rays were distinctive to each element.
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By taking the X-ray frequencies found in the experiment, finding their square root, and plotting this on a graph next to the corresponding element's atomic number, Moseley found it made a straight line. Simply put, this meant that an element's atomic number matched the charge, or amount of protons, it had; thus, when Moseley put elements in the order of their number of protons rather than their atomic masses, the incorrect order of elements that had previously been seen was nonexistent. This declared the hypothesis by Antonius van den Broek to be correct.

History of Periodic Table
Two additional observations were made by Moseley during his proving of Antonius van den Broek's hypothesis. The first was that there were four gaps in the new version of the periodic table; this finding had previously been noted by Mendeleev and would help four new elements to eventually be discovered. The second observation was that any element could be recognized by using Moseley's method of shooting electrons at it and finding the resulting X-ray frequency.

Article Regarding Moseley's Death

While his colleagues begged he do otherwise, Moseley enlisted in the army during World War I, only a year after helping create the new periodic table. He was killed roughly a year later on August 10, 1915. Following his death, the British Government stated that scientists of merit were banned from enlisting in front-line military roles. Additionally, no Nobel Prizes were given in the year of 1916, presumably as a result of Moseley's death.
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Physicist Henry Moseley had a strong impact on the atomic theory as he assisted in perfecting the periodic table. Without his experiments which involved using X-ray frequencies and electrons to determine the number of protons in an atom, the periodic table might have never been made correct. Moseley assisted in our understanding of atomic structure, element identification, the order of the periodic table and, ultimately, the atomic theory.

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