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Models of the Atom:

Models of the Atom:. a history. The Atom’s History……. Recognized 4 major elements: Fire Earth Water Air. Democritus (4th century BC) Greece. Believed that matter was composed of tiny indivisible particles called atoms (“indivisible”) Based on philosophy NOT experimentation .

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Models of the Atom:

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  1. Models of the Atom: a history

  2. The Atom’s History……

  3. Recognized 4 major elements: • Fire • Earth • Water • Air

  4. Democritus (4th century BC) Greece • Believed that matter was composed of tiny indivisible particles called atoms (“indivisible”) • Based on philosophy NOT experimentation

  5. John Dalton • Came up with a 5-part atomic theory • Most of his findings still hold true today

  6. All elements are composed of submicroscopic, indivisible particles called atoms Atoms of the same element are identical. Atoms of different elements are not the same. Atoms of different elements can physically mix together or can chemically combine with one another in simple whole-number ratios to form COMPOUNDS. Chemical reactions occur when atoms are separated, joined or rearranged. Atoms of one element are never changed into atoms of another element. Atoms cannot be subdivided, created or destroyed. #5has changed because of the discovery of the proton, neutron, and electron #2has been modified because of isotopes. Dalton’s Atomic Theory

  7. Thomson discovered the electron, realized atoms were not indivisible • Revise atomic model: “plum pudding model” • A ball of + charge containing a number of electrons

  8. Pros: Explained some electrical properties of atoms Cons: Doesn’t discuss # of protons or neutrons Their arrangements in atom How electrons are stripped to form ions Thomson model

  9. Dense nucleus of protons/neutrons - electrons in empty space around it

  10. Pros: Explains # protons/neutrons, arrangement, and e- stripping Cons: Opposite charged particles attract each other, what keeps e- in place? Rutherford model

  11. Bohr Model • Electrons in each energy level have a fixed energy - quantum • Quantized energy levels - • Fixed amt of energy required to move from 1 energy level to another • like the rungs of a ladder • Cons: • only works perfectly for Hydrogen

  12. Quantum Model(Current)

  13. Quantum Model • Describes electrons as waves confined to a specific shape • Orbitals – define the shapes where electrons exist • Incorporates the Heisenberg Uncertainty Principle and the Schrodinger Wave Equation

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