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350
Aristotle
Aristotle created the scientific method:
Observation
Hypothesis
Experiment
Conclusion
Theory -
Period: 350 to
Atomic Theory
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460
Democritus
Democritus claimed that everything is made up of atoms, and that these atoms are indivisible. He claimed that there was empty space in between each of the atoms, and that they all weighed the same. He said there were infinite numbers and shapes of atoms; like the salt atom, which was pointed and small, and the air atom, which was light and whirling. Most of his theories were wrong. -
Isaac J Newton
Newton suggested that atoms were held together by attractions that we call forces. -
John Dalton
He proved the existence of atoms. 1-- All matter is made of atoms. Atoms are indivisible and indestructible.
2-- All atoms of a given element are identical in mass and properties
3-- Compounds are formed by a combination of two or more different kinds of atoms.
4-- A chemical reaction is a rearrangement of atoms. -
Dmitri Mendeleev
Arranged elements into 7 groups with similar properties. Dmitri discovered that the properties of elements "were periodic functions of their atomic weights". This became known as the 'Periodic Law'. -
J. J. Thomson
He proved that atoms could be seen, that they weren' invisible. Thomson claimed that the model of an atom was a sphere of positively charged matter with negatively charged electrons surrounding them. -
Ernest Rutheford
Ernest believed that an atom was mostly empty space. He believed the atom had a central nucleus. This nucleus was surrounded by electrons that were negative and orbited the atom. -
Neil Bohr
Neil contributed to the Atomic Theory by stating that electrons travel around an atomic nucleus in a stationary orbit. His work also led to the theory of different energy levels in atoms, that is if an electron drops from a higher to a lower orbit, it must release energy. -
James Chadwick
When he was using alpha particles he discovered a neutral atomic particle with a mass close to a proton.
