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Models of the Atom: a history. The Atom’s History……

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Presentation on theme: "Models of the Atom: a history. The Atom’s History……"— Presentation transcript:

1 Models of the Atom: a history

2 The Atom’s History……

3 Recognized 4 major elements: -Fire -Earth -Water -Air

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

5 John Dalton -Came up with a 5- part atomic theory -Atoms are tiny, solid, indivisible spheres of matter

6 Dalton’s Atomic Theory No, you don’t need to write all of this… just FYI 1. All elements are composed of submicroscopic, indivisible particles called atoms 2. Atoms of the same element are identical. Atoms of different elements are not the same. 3. Atoms of different elements can physically mix together or can chemically combine with one another in simple whole- number ratios to form COMPOUNDS. 4. Chemical reactions occur when atoms are separated, joined or rearranged. Atoms of one element are never changed into atoms of another element. 5. Atoms cannot be subdivided, created or destroyed. #5 has changed because of the discovery of the proton, neutron, and electron #2 has been modified because of isotopes.

7 Dalton’s model  Pros: –Most of the atomic theory is still valid today  Cons: –Thought atoms were indivisible (no p, e, n) –No mention of ions or isotopes

8  Thomson discovered the electron, realized atoms were not indivisible  Revised atomic model: “plum pudding model”  A ball of + charge containing a number of electrons

9 Thomson model Pros: –Explained some electrical properties of atoms Cons: –Doesn’t discuss # of protons or neutrons –How are e- arranged? –How are electrons stripped to form ions?

10  Dense nucleus of protons/neutrons - electrons in empty space around it

11 Rutherford model Pros: –Explains # protons/neutr ons, arrangement, and e- stripping Cons: –Opposite charged particles attract each other, what keeps e- in place?

12

13 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

14 Quantum Model (Current)

15 Quantum Model  Describes electrons as waves confined to a specific shapes (Incorporates the Heisenberg Uncertainty Principle and the Schrodinger Wave Equation) –Energy Levels + S, P, D, and F orbitals for electrons –Orbitals – define the shapes where electrons exist around the nucleus  Cons: ??? (working pretty good so far!)


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