NATS 1760 Lecture Notes - Lecture 7: Thorium, Mass Number, Exponential Decay
14 Nov 2013
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Document Summary
Proton: one unit of positive electric charge. Gravitational: weak; only good for very large things. Nuclear: short-range; acts between nucleons; always attractive. A nucleus surrounded by a number of electrons (typically equal to the protons in the nucleus) A single atom; behaves in a chemically unique way (according to electron number) Nuclei of the same element that have different numbers of neutrons (and different masses) To be radioactive is to contain unstable nuclei. A helium-4 (he) particle is spat out (2 protons (+), 2 neutrons (n)) Large mass but low speed = easy absorption. Typically a neutron (n) turns into a proton (+) & an electron (-), and the electron (-) is ejected. Smaller mass than he, but higher speed. A nucleus acquires excess energy (via impact with a particle) and in its excited state stores energy before emitting a high-energy photo quite suddenly.
