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Atomic Theory Timeline

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Presentation on theme: "Atomic Theory Timeline"— Presentation transcript:

1 Atomic Theory Timeline
Development of our understanding of the atom

2 Early Models Democritus was first to suggest atom in 4th century B.C.
Dalton’s model was the “Billiard Ball” Atomic Theory Matter is composed of atoms Atoms are indivisible Atoms of a given element have same size, mass and chem props and are different from those of another element Different atoms combine in whole number ratios to form compounds and are separated, combined and rearranged in chem reactions Conservation of Mass

3 Early Models Thomson used the Cathode Ray – determined atoms were made of particles Negative charges in atom “Plum Pudding” model Millikan used oil drop experiment Found mass and charge of an electron

4 Important discoveries
Rutherford experimented with Gold Foil Found nucleus Discovered its positive charge and tiny size Electrons moving around the nucleus Came up with “Nuclear Model”

5 Moving Forward… Bohr said electrons move in orbits
Found in energy levels Explains bright-line spectrum Called “Planetary Model” But Bohr knew that it was flawed

6 What we believe now Orbital proposed by Schrödinger
Describes most likely where electrons were Quantum mechanics new theory “Electron Cloud” model

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