University:
University of Pennsylvania
Course:
CHEM 1011 | Introduction to General Chemistry I
Academic year:

2023
Views:

150

Pages:

2
Author:

esfredint7qo

Atomic Theory Timeline Democritus John Dalton Michael Faraday J. J. Thomson Robert Millikan Ernest Rutherford ~450 BC 1803 1839 1896 1909 1909 Greek philosopher English schoolteacher English chemist English physicist American physicist University of Chicago New Zealand scientist All matter around us is made of indivisible tiny particles“atomos” (p.91) Dalton’s Atomic Theory 1) Elements are made of tiny particles called atoms. 2) Atoms of one element are identical while atoms of different elements are different. 3) Conservation of atoms— rearrangement in RXN (Lavoisier previously stated this in terms of the Law of Conservation of Matter) 4) Different atoms form compounds in constant ratios. (Proust previously stated this in terms of the constant mass ratios) (p.92) The structure of atoms is somehow related to electricity. Discovered atoms have negative particles (electrons) using a cathode ray tube. Measured the charge of an electron using oil droplets. (p.95) Discovered electron’s charge to mass ratio: 1.76 x 108 C/g Electron’s charge: 1.60 x 10-19 C (p. 97-98) Thomson’s Plum Pudding Model, 1900 Electron’s mass: 9.11 x 10-28 g + (p. 100-102) *1919- named positive charge the proton (+1) *1932- Rutherford and James Chadwick discover neutron in nucleus (no charge) + - + + + - + - + - + + + *Most of an atom is empty space (p. 98) Electrons are dispersed in a uniform positive charge. (p. 62 & 101) - Rutherford’s Nucleus Theory Positive charge is not like a pudding, but concentrated in the nucleus as shown in the Gold Foil (alpha particle) experiment Versus +5 - - - Atomic Theory Timeline Henry Moseley Niels Bohr (1887-1915) 1911 Louis de Broglie & (Schrödinger) 1924 English scientist Rutherford student Moseley’s Atomic # Each element contains a unique number of protons. (atomic #) Danish physicist French graduate student Bohr’s Orbit Model *Electrons orbit the nucleus. *Model based on the hydrogen atom *Energy of the electrons is quantized. Wave Mechanical Model *Electrons can act like particles and waves (just like light) *Electrons occupy orbitals. Orbitals are nothing like orbits. They are areas of probability (90% of electron probability) *Clinton Davisson and Lester Germer performed experiments to support the wave mechanical model. (p. 104) (p. 136-138) + S orbital P. 142 P orbital P. 142 D orbital P. 145

Atomic Theory Timeline: Evolution of the Atomic Model

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