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Thanks to all that answered. Vascop, the first link you posted was simple and answered all I was after. The second link you posted was the article I had been reading. I think that Jake-the-peg has it right, the original definition was an over simplification, or just plain misleading. As for the isotope definition, this again is an over simplification. Perhaps a better definition would be: Isotopes are different types of atoms (nuclides) of the same chemical element, each having a different number of neutrons from the stable state of that element.
Thanks again.