CHEM 11100 Lecture Notes - Lecture 2: Cathode Ray, Parmigianino, Electric Field

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Early atomic theory: democritus: matter exists in form of particles; coined atoms , alchemists (~1000-1650): tried to turn lead into gold, aristotle, newton, roger bacon, aquinas, brahe, thomas browne, parmigianino attempted to explain matter. Modern atomic theory: dalton"s atomic theory of 4 postulates in new system of chemical philosophy (1808) Structure of the atom: mid 1850s: cathode rays (electric discharge through partially evacuated tubes, j. j. thompson: electric field causes rays to bend; therefore, rays are negatively charged particles. Plum-pudding model: electrons embedded in a positive charge. Thompson"s experiment (1897: use of electric and magnetic (e and b, respectively) fields to measure the charge to mass (q/m) ratio of an electron, q/m = e2/(2vb2) 1. 759 x 1011 c/kg. Formula for q/m ratio: velocity of beam: (1/2)mv2 = qv; v = velocity; v = voltage, balance e and b forces: qe = qvb.