Presentation on theme: "Atomic Theory Timeline"— Presentation transcript:
1 Atomic Theory Timeline Development of our understandingof the atom
2 Early Models Democritus was first to suggest atom in 4th century B.C. Dalton’s model was the “Billiard Ball”Atomic TheoryMatter is composed of atomsAtoms are indivisibleAtoms of a given element have same size, mass and chem props and are different from those of another elementDifferent atoms combine in whole number ratios to form compounds and are separated, combined and rearranged in chem reactionsConservation of Mass
3 Early ModelsThomson used the Cathode Ray – determined atoms were made of particlesNegative charges in atom“Plum Pudding” modelMillikan used oil drop experimentFound mass and charge of an electron
4 Important discoveries Rutherford experimented with Gold FoilFound nucleusDiscovered its positive charge and tiny sizeElectrons moving around the nucleusCame up with “Nuclear Model”
5 Moving Forward… Bohr said electrons move in orbits Found in energy levelsExplains bright-line spectrumCalled “Planetary Model”But Bohr knew that it was flawed
6 What we believe now Orbital proposed by Schrödinger Describes most likely where electrons wereQuantum mechanics new theory“Electron Cloud” model
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