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  2. History of atomic theory - Wikipedia

    en.wikipedia.org/wiki/History_of_atomic_theory

    The term "compound atom" was confusing to some of Dalton's contemporaries as the word "atom" implies indivisibility, but he responded that if a carbon dioxide "atom" is divided, it ceases to be carbon dioxide. The carbon dioxide "atom" is indivisible in the sense that it cannot be divided into smaller carbon dioxide particles. [4] [19]

  3. Discovery of chemical elements - Wikipedia

    en.wikipedia.org/wiki/Discovery_of_chemical_elements

    De Boisbaudran found a new earth in erbia. [147] 18 Argon: 1894 Lord Rayleigh and W. Ramsay: 1894 Lord Rayleigh and W. Ramsay They discovered the gas by comparing the molecular weights of nitrogen prepared by liquefaction from air and nitrogen prepared by chemical means. It is the first noble gas to be isolated.

  4. J. J. Thomson - Wikipedia

    en.wikipedia.org/wiki/J._J._Thomson

    Thomson in 1897 was the first to suggest that one of the fundamental units of the atom was more than 1,000 times smaller than an atom, suggesting the subatomic particle now known as the electron. Thomson discovered this through his explorations on the properties of cathode rays.

  5. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    Thomson later found that the positive charge in an atom is a positive multiple of an electron's negative charge. [23] In 1913, Henry Moseley discovered that the frequencies of X-ray emissions from an excited atom were a mathematical function of its atomic number and hydrogen's nuclear charge.

  6. Timeline of atomic and subatomic physics - Wikipedia

    en.wikipedia.org/wiki/Timeline_of_atomic_and...

    1897 J. J. Thomson discovered the electron; 1897 Emil Wiechert, Walter Kaufmann and J.J. Thomson discover the electron; 1898 Marie and Pierre Curie discovered the existence of the radioactive elements radium and polonium in their research of pitchblende; 1898 William Ramsay and Morris Travers discover neon, and negatively charged beta particles

  7. Ernest Rutherford - Wikipedia

    en.wikipedia.org/wiki/Ernest_Rutherford

    He found that nitrogen, and other light elements, ejected a proton, which he called a "hydrogen atom", when hit with α (alpha) particles. [23] In particular, he showed that particles ejected by alpha particles colliding with hydrogen have unit charge and 1/4 the momentum of alpha particles.

  8. For the First Time Ever, Scientists Have Witnessed the Birth ...

    www.aol.com/first-time-ever-scientists-witnessed...

    According to the press release, when the universe was first born and full of ionized plasma, it took a full 370,000 years for conditions to cool enough for atoms to form and for light to start ...

  9. History of molecular theory - Wikipedia

    en.wikipedia.org/wiki/History_of_molecular_theory

    In two papers outlining his "theory of atomicity of the elements" (1857–58), Friedrich August Kekulé was the first to offer a theory of how every atom in an organic molecule was bonded to every other atom. He proposed that carbon atoms were tetravalent, and could bond to themselves to form the carbon skeletons of organic molecules.