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Transcript of Atomic Models
by Georges Seurat Democritus 430 BC Greek philosopher
Proposed the idea that matter is formed of small pieces that could not cut into smaller parts.
He called these pieces atomos, which means “uncuttable”. Atomic Theory Atomic theory grew as a series of models that developed from experimental evidence.
As more evidence was collected, the theory and models were revised. Dalton’s Atomic Theory 1600’s Dalton thought that atoms were like smooth, hard balls that could not be broken into smaller pieces. Thomson Model 1897 JJ Thomson suggested that atoms had negatively charged electrons embedded in a positive sphere. Ernest Rutherford’s Model 1911 According to Rutherford’s model, an atom was mostly empty space.
The atom was mostly empty space with electrons moving around the nucleus. Niels Bohr’s Model 1913 Bohr suggested that electrons move in specific orbits around the nucleus of an atom. Cloud Model 1920’s According to the cloud model, electrons move rapidly in every direction around the nucleus.
An electron’s movement is related to its energy level. Modern Atomic Model 1932 The modern atomic model describes an atom as consisting of a nucleus that contains protons and neutrons, surrounded by a cloudlike region of moving electrons. Rutherford's Gold Foil Experiment:
Rutherford noticed that a few particles were deflected strongly when he shot a beam of positively charged particles at a piece of gold foil.
Rutherford proposed an atomic model with a positively charged nucleus.