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430
Democritus' Model
Democritus' atomic theory asked the question as to "Does matter keep getting broken apart forever, or is there something in matter that is indivisible? His theory was that there was an indivisible particle which he called the "atomos" or Atom. He viewed atoms as infinite in number, but different shapes and sizes, and were made of the same material. Democritus had spent his entire life in Greece. -
Period: 460 to
History of the Atomic Theory
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Dalton's discovery
In Dalton's view: Atoms were indivisible, and all matter is made up of these atoms; a chemical reaction is of a combination of these atoms; compounds are formed from different combinations of these atoms; and atoms cannot be created or destroyed. John Dalton was born in the United Kingdom, and his atomic theory was based off of observational experiments -
J.J. Thomson's Atomic Theory
Thomson was born in Manchester England. His experiments had changed the Atomic Theory forever. Thomson had discovered what is called an electron, which was a negatively charged particle found in the atom, which then disproved the theory on how the atom was indivisible. He thought the atom consisted of a sphere of positive charge with negatively charged electrons embedded within it. And there were an equal number, making the atom neutral charge. -
Max Planc
Planc was born in Germany, His work in thermodynamics led him to his formulations of Quantum Theory. To explain the colors of hot glowing matter, he proposed that energy is radiated in very minute and discrete quantized amounts or packets, rather than in a continuous unbroken wave. Planck called the packets of energy quanta and he was able to determine that the energy of each quantum is equal to the frequency of the radiation multiplied by a constant, known as Planc's Constant. -
Rutherford's Atomic Theory
Based on Rutherford's experiments, he had created an accurate model of the atom and what was inside it. In his experiment he noticed that the atom had almost all of it's mass concentrated at a small point in the center, which was later called the nucleus of the atom. He also discovered, in 1909, that the electrons relatively speaking; were at an incredibley far distance compared to where the nucleus was in the atom. -
Niels Bohr
Neils Bohr had refined Rutherford's model by discovering that electrons orbit the nucleus WITHOUT losing energy; and electrons with low energy would orbit closer to the nucleus, whilst electrons with high energy orbit further from the nucleus. Though Bohr had discovered these things, there were still questions liked "Why don't electrons give off light all the time" or "why shouldn't electrons be confined to only one of their energy levels?" -
Werner Heisenberg
Heisenberg was born in Germany, in 1901. His most revolutionary discoveries was his 'Uncertainty Principle' which stated that you couldn't know an electrons state, whether it acted as a wave, or as a particle. It also showed that you cannot know the path or patterns of the electron's movements orbiting around the nucleus. -
Chadwick's discovery
James Chadwick, whom was born in the United Kingdom had made the revolutionary discover of the neutron. This particle had significant mass, but no charge - neutral charge. With this discovery came once again; a refined atomic model of the atom. It now composed of the Neutrons and Protons in the nucleus, and the electrons whirling around the nucleus of the atom.
