Atomic Theory - B PDF
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This document provides information on atomic theory, covering topics like the atomic number, mass number, isotopes, and the different scientists who contributed to our understanding of atoms. It also explains the mass spectrometer. The text also delves into the different experiments.
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Atomic Theory – B The atomic number is the number of protons in the nucleus of that atom. The mass number is the sum of the number of protons & neutrons in the nucleus. Isotopes are atoms with the same number of protons but di erent numbers of neutrons. The relative atomic mass (Ar) is the a...
Atomic Theory – B The atomic number is the number of protons in the nucleus of that atom. The mass number is the sum of the number of protons & neutrons in the nucleus. Isotopes are atoms with the same number of protons but di erent numbers of neutrons. The relative atomic mass (Ar) is the average mass of an atom of the element relative to 1/12 the mass of an atom of carbon-12. 1. John Dalton: a. All matter is made up of very small particles called atoms. b. All atoms are indivisible – they cannot be broken into simpler particles. c. Atoms cannot be created or destroyed in the course of a chemical reaction (known as the Law of Conservation of Mass) 2. William Crooke: a) He called these rays cathode rays as they came from the negative terminal. b) He conducted the Maltese Cross experiment 3. JJ Thomson: a) ∴Thomson concluded that cathode rays/ z electrons they were negatively charged. b) ∴ Thomson concluded that sub-atomic particles existed. 4. Johnstone Stoney: He suggested the name electron for these negatively charged particles. 5. Robert Milikan: oil drop experiment, charge on an electron. 6. Ernest Rutherford: the α–particle scattering experiment. a) A large number of α-particles were not deflected at all. b) Many particles were deflected at small angles. c) A small number of particles were deflected at angels greater then 90°. d) A smaller number bounced back towards their source. 7. Neils Bohr: Bohr model 8. James Chadwick: discovered the existence of neutrons Mass Spectrometer Principle: The mass spectrometer works on the principle that ions can be separated according to their mass. The lighter the ion, the more it will be deflected by a magnetic field. Processes: Vaporisation, Ionisation, Acceleration, Seperation, Detection
