CHM1011 Lecture Notes - Lecture 1: Atomic Number, Cathode Ray, Ernest Rutherford
31 Jul 2018
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In 1897 j. j. thomson discovers cathode rays in a discharge tube these rays are a stream of negatively charged particles called electrons. Becquerel and the curies (marie and pierre) investigate radioactivity. 3 different types of radiation are then discovered by ernest rutherford. +ve charge resides in an extremely tiny dense nucleu s most of the total volume of the atom is empty space in which the electrons move. Subatomic particles: protons and electrons are the only particles that have a charge, protons and neutrons have essentially the same mass, the mass of an electron is only ~ 1/2000 of the mass of the heavy particles . The number of protons in the nucleus of an atom of any particular element is called that element"s atomic number (z). The mass number (a) of an atom is the total number of protons plus neutrons in that atom.
