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Atomic Theory Timeline Development of our understanding of the atom

Atomic Theory Timeline Development of our understanding of the atom

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Page 1: Atomic Theory Timeline Development of our understanding of the atom

Atomic Theory Timeline

Development of our understanding

of the atom

Page 2: Atomic Theory Timeline Development of our understanding of the atom

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

Page 3: Atomic Theory Timeline Development of our understanding of the atom

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

Page 4: Atomic Theory Timeline Development of our understanding of the atom

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”

Page 5: Atomic Theory Timeline Development of our understanding of the atom

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

Page 6: Atomic Theory Timeline Development of our understanding of the atom

What we believe now

Orbital proposed by Schrödinger Describes most likely where electrons were

Quantum mechanics new theory “Electron Cloud” model