why isn't information about the mass of an isotope sufficient for identifying an isotope? Provide an example.

Question

jfraser · Answer

simply knowing how much a particular atom weighs isn't enough to identify the atom itself. One isotope of carbon may have 6 protons, 8 neutrons, and a mass of 14. An isotope of nitrogen (right next door on the PT) may have 7 protons and 7 neutrons, also for a total mass of 14. If all you know is the mass, you really don't know anything at all

anonymous · Answer

An isotope of a certain element can have multiple mass #s. The atomic number, which identifies the element by the number of protons is the only way to positively id what element the isotope belongs to. For example, Mg has 3 isotopes, mass numbers 24, 25 and 26. But if you tell me the atomic number is 12, that is the only way I know for sure we are talking about Mg. If you just give me the mass numbers 24, 25 or 26, I don't know what element it is.