atomic numbers. henry moseley (1887 - 1915) “moseley, as it were, called the roll of the elements,...
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Atomic Numbers
Henry Moseley (1887 - 1915)
“Moseley, as it were, called the roll of the elements, so that for the first time we could say definitely the number of possible elements between the beginning and the end, and the number that still remained to be found.”
Ions in Water Solution
Mass Spectra
Mass Spectroscope
Francis William Aston (1877 - 1946)
Modern Mass Spectroscope
Hydrogen Spectrum
Atomic Weights of Some IsotopesElement Isotope Atomic Weight
Hydrogen 1H 1.0078252H 2.01410
Helium 4He 4.0026
Carbon 12C 12 (exactly)13C 13.00335
Oxygen 16O 15.9949117O 16.9991
Neon 20Ne 19.9924421Ne 20.9939522Ne 21.99138
Chlorine 35Cl 34.9688537Cl 36.9659
Uranium 235U 235.0439238U 238.0508
Mass Number (A) Isotopic Mass (amu) % Abundance
196 195.165 0.14
198 197.967 10.04
199 198.967 16.83
200 199.968 23.12
201 200.970 13.23
202 201.970 29.79
204 203.973 6.85
Mercury Spectrum
Atomic Number
Atomic Weight
Atomic Structure
Worked with:Hans GeigerErnest Marsden
Ernest Rutherford (1871 - 1937)
Gold Foil Experiment
Then I remember two or three days later Geiger coming to me in great excitement and saying, “We have been able to get some ofthe alpha particles coming backwards…” It was quite the mostincredible event that has ever happened to me in my life. It wasalmost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it cam back and hit you.
Radioactive Elements
Pitchblende
Pierre and Marie Curie
Large Nuclei