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Period: 400 to
(The start date is actually B.C.)
(The start date is actually B.C.) -
460
Greek philosopher Democritus develops the idea of atoms.
He asked this question: If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? Democritus thought that it ended at some point, a smallest possible bit of matter. He called these basic matter particles, atoms. -
English Chemist John Dalton discovers atoms do exist.
John Dalton performed experiments with various chemicals that showed that matter, indeed, seem to consist of elementary lumpy particles (atoms). Although he did not know about their structure, he knew that the evidence pointed to something fundamental. -
English physicist J.J. Thomson discovers the electron.
He also proposed a model for the structure of the atom. Thomson knew that electrons had a negative charge and thought that matter must have a positive charge. His model looked like raisins stuck on the surface of a lump of pudding. -
Ernest Rutherford discovers electron behavior.
Ernest Rutherford discovers that electrons don't merely sit in a glob of positively charged matter, but orbit around a tiny bit of positively charged matter. He was the discoverer of the fact that atoms are mostly empty space. -
Danish physicist Niels Bohr creates planetary model.
In 1912 a Danish physicist, Niels Bohr came up with a theory that said the electrons do not spiral into the nucleus, but spiral around it, similar to a solar system. -
Austrian physicist Erwin Schrödinger discovers quantum physics model.
Austrian physicist Erwin Schrödinger expanded on Louis de Broglie's thought about particles of matter: He thought that if light can exist as both particles and waves, why couldn't atom particles also behave like waves? Schrodinger expanded by forming a model of the atom on that basis. It is his model that is still commonly used today, with the electrons' paths being shown around the atom, making the atom look like an invisible ball with rubber bands wrapped around it. -
Quarks
The most recent discoveries of the atom have been with quarks. In 1964 Murray Gell-Mann proposed the existence of a new level of elementary particles and called them "quarks" (the spelling derives from a phrase in James Joyce book, Finnegans Wake, "Three quarks for Muster Mark." Gell-Mann thought there existed at least three types of quarks. They have the names, "up," "down," and "strange." From 1974 thru 1984 the theory predicted three more quarks called "charm," "bottom", and "top". -
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