Henry Moseley Looking Inside the Nucleus A Presentation by Xavier Norman, Serena Locke, and Violet Kertis

Biography Born November 23, 1987 died August 10, 1915 Born in Weymouth, England Parents named Henry and Amabel Henry (his father)- professor: anatomy and physiology Amabel (his mother)- mollusk biologist Full name: Henry Gwyn Jeffreys Moseley

The Atom Previously Rutherford had just confirmed the existence of the nucleus in the atom and Bohr had just used this model in his theory of the optical spectrum of atomic hydrogen. Ernest Rutherford

Experimental Design Moseley devised an experiment in which he bombarded samples of every element from aluminum to gold (that were available at the time) and measured the wavelengths and frequencies. He used x rays to determine to different properties of the elements.

The Experiment (in depth) Henry put specimen in a x-ray tube From there he would create x-rays of the specimen and analyze them with a spectrometer Used induction coil for power Then created a vacuum in the x-ray tube and spectrometer Knew that when electrons hit an element, characteristic wavelengths were created Because the wavelengths were different, dissimilar angles were reflected from the crystal center of the spectrometer X-ray beams then hit photographic plate. Lines were created once the rays hit it. The angles and positions and separation of these lines varied for every element. Henry could now find the wavelengths of the beams using a certain equation (Slide 4) and the number of protons in the nucleus for each element.

What Did Moseley’s Experiment Accomplish? Mosley’s experiment was significant due to: The dependence of the square root of the frequencies could be explained in terms of the Bohr theory, by applying it to the innermost electrons in the atom, rather than the outermost, as Bohr had done. There were gaps in the plot (43, 61, and 75) that turned out to be elements that were not even discovered yet. (technetium, promethium, and rhenium) The elements in any solid sample could be identified by measuring the spectrum of the X-rays it emits (which is now used as a method of non-destructive analysis). Moseley was able to elaborate on the specifics of the nucleus. Henry discovered that an element's identity is based on the number of protons in the nucleus.

The Evidence With Moseley’s research and the discovery or isotopes of an element, it became clear that atomic weight was not the significant player in the periodic law as Mendeleev, Meyers and others had thought, but instead, the properties of the elements varied periodically with atomic number When atoms are arranged according to the atomic number, the problems with Mendeleev's theory were resolved. Moseley’s research is the reason that the modern periodic table is based on the atomic number of the elements.

The New Atomic Model Moseley's research proved that the proton count within an atom increases by regular steps, in a linear fashion, as we pass from one element to the next.

Interesting Tidbits!! Won a scholarship for Eston College (high school) when he was only in elementary school Was awarded with Eton’s physics and chemistry prizes (Age 18) Won Nobel Prize in Chemistry for discoveries (radioactivity) Was rather shy and reserved Did not like teaching and preferred independent work Only lived to age 27 :( (died at war)

Works Cited Slide 1 & Slide 7 Slide 3 Slide 3 & Slide 3 Slide Slide 4&5 Slide 7 Slide Slide 1