Eventos
First Mention of elements with different numbers of neutrons (neutrons not discovered yet)Isotopes DiscoveredNobel PrizeNiels Bohr publishes theory of atomic structure, combining nuclear theory with quantum theory.English chemist Frederick Soddy in 1910 observed that “elements of different atomic weights [now called atomic masses] may possess identical (chemical) propertiesby 1935 the principal isotopes and their relative proportions were known for all but a handful of elementsthe gaseous element neon produced two positive rays. The ions in the heavier ray had masses about two units, or 10 percent, greater than the ions in the lighter ray. To prove that the lighter neon had a mass very close to 20 and that the heavier ray was indeed neon and not a spurious signal of some kind. Comfirmed isotopesHydrogen, much helium, and some lithium isotopes are thought to have formed at the time of the big bangIn 1914 T. W. Richards found variations between the atomic weight of lead from different mineral sources, attributable to variations in isotopic composition due to different radioactive originsAtomic Bomb uses radioactivity
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