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THE ATOM

THE ATOM. Around 400 B.C. a Greek philosopher, Democritus , proposed that all forms of matter were divisible into extremely small fundamental particles called atomos . (Greek for indivisible)

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THE ATOM

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  1. THE ATOM • Around 400 B.C. a Greek philosopher, Democritus, proposed that all forms of matter were divisible into extremely small fundamental particles called atomos. (Greek for indivisible) • Due to world events, this concept was forgotten, replaced by the belief that matter was composed of four “elements” ; earth,wind, fire, & water. • From 1803 to 1810, John Dalton proposed the concept of the atom once again. Dalton backed his claim with experimentation.

  2. The modern atom is composed of subatomic particles.

  3. Subatomic Particles • ELECTRON: Properties discovered in 1897 by JJ Thompson • PROTON: Isolated and identified in 1919 by Ernest Rutherford • NEUTRON: Discovered by James Chadwick in 1932

  4. Nuclear Model of the Atom • Every atom contains an extremely small, extremely dense nucleus. • All of the positive charge and nearly all of the mass of an atom are concentrated in the nucleus. • The nucleus is surrounded by a much larger volume of nearly empty space that makes up the rest of the atom. • The space outside the nucleus is very thinly populated by electrons, the total charge of which exactly balances the positive charge of the nucleus.

  5. may come in one of three forms:

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