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Atomic Timeline John Michael J. J. Thomson Robert Millikan

~450 BC 1803 1839 1896 1909 1909

Greek English schoolteacher English English American physicist New Zealand All Dalton’s The structure of Discovered have Measured the Rutherford’s around us is atoms is negative particles charge of an Nucleus Theory made of 1) Elements are made of somehow related () using a using oil Positive charge is not indivisible tiny tiny particles called to . ray tube. droplets. like a pudding, but particles- atoms. concentrated in the “atomos” (p.95) Discovered electron’s Electron’s charge: nucleus as shown in 2) Atoms of one element are charge to ratio: 1.60 x 10-19 C the Gold Foil (alpha (p.91) identical while atoms of 1.76 x 108 C/g particle) experiment different elements are Electron’s mass: different. (p. 97-98) 9.11 x 10-28 g *Most of an is empty space 3) Conservation of atoms— Thomson’s Plum (p. 98) rearrangement in RXN Pudding Model, 1900 (p. 100-102) (Lavoisier previously stated this in terms of the Law of Electrons are dispersed in *1919- named positive Conservation of Matter) a uniform positive charge. charge the (+1) (p. 62 & 101) *1932- Rutherford and 4) Different atoms form compounds in constant + - discover in - ratios. nucleus (no charge) + - (Proust previously stated this + - + in terms of the constant mass - + - ratios) (p.92) - + - - - Versus +5 + + - - - - + + - Atomic Theory Timeline Moseley & (Schrödinger) (1887-1915) 1911 1924

English scientist Danish physicist French graduate student Rutherford student Moseley’s Atomic # Bohr’s Model Mechanical Model Each element *Electrons orbit the *Electrons can act like contains a unique nucleus. particles and (just number of . *Model based on the like ) (atomic #) atom *Electrons occupy *Energy of the orbitals. Orbitals are (p. 104) electrons is quantized. nothing like . They are areas of (p. 136-138) (90% of electron probability) * and performed experiments to support the + wave mechanical model.

S orbital P. 142

P orbital P. 142

D orbital P. 145