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Transcript
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 John Dalton - Came up with a 5part atomic theory - Atoms are tiny, solid, indivisible spheres of matter Dalton’s Atomic Theory No, you don’t need to write all of this… just FYI 1. 2. 3. 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 wholenumber 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. 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. 4. 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 Thomson discovered the electron, realized atoms were not indivisible Revised atomic model: “plum pudding model” A ball of + charge containing a number of electrons Thomson model Pros: – Explained some electrical properties of atoms Cons: – Doesn’t discuss # of protons or neutrons – How are earranged? – How are electrons stripped to form ions? Dense nucleus of protons/neutrons - electrons in empty space around it Rutherford model Pros: – Explains # protons/neutrons, arrangement, and e- stripping Cons: – Opposite charged particles attract each other, what keeps ein place? 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 Quantum Model (Current) 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!)