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500 BCE
Meet Democritus
The atomic theory started in Ancient Greece by the materialist philosopher Democritus. Democritus stated that all matter is made up of units that move. He called them atomos, meaning uncuttable in Greek -
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John Dalton's Atomic Theory
There are a few important rules that came about in the late 1700's that were crucial to Dalton's thoughts. First was the 'Law of Conservation of Mass', formulated by Lavoisier. This stated that whatever the quantity of substance you take, the proportions of the masses of elements composing this substance will always remain equal. In attempt to explain how and why elements would combine in fixed ratios and multiply he formulated his Atomic Theory. -
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JJ Thomson's Discoveries
Scientist's began to realise that the atom was made up of subatomic particles that were thought to be positively and negatively charged. JJ Thompson observed that opposite charges attract each other and like charges will repel. He suggested that negative charges were balanced by a positive umbrella charge. this model is referred to as the "plum pudding model". -
Ernest Rutherford "The Father of Nuclear Physics"
Rutherford was Thomson's student and widely known for the Gold Foil Century. This experiment was simple - take a really thick foil of gold, a few atoms thick and bombard it with positively charged alpha particles. Acording to the model proposed by Thomson, the particles should pass through undisturbed. In 1911, Rutherford published a solution which stated that atoms aren't made of electrons with positive dough around them. -
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Ernest Rutherford "The Father of Nucleus Physics"
Based on this work and contributions from other scientists, Rutherford developed a new model fro the atom. This model introduced the nucleus - a centre where the majority of the atom's mass and charge located. This model of the atom is pretty much what we use today.