And how do scientists measure the average amount of molecular mass for each atom, they cant check every atom of the particular element in the universe to determine its molecular mass , and if scientists take samples from areas rich in a particular type of isotopes, wouldnt it affect the total average molecular mass of an element.
In: Chemistry
Elements are produced by various means in nature, some of which are stable, some of which are not, and the mixture of not-stable isotopes with stable isotopes is very predictable. This is the reason why atomic weights on the periodic table are an average value, not a specific integer number as you might expect.
Let’s take a very well known example for this. The molecular weight of the most stable isotope of carbon is 12. But you’ve no doubt heard of Carbon-14. C14 is constantly being produced in the atmosphere by the action of cosmic rays on nitrogen – when nitrogen (7 protons) interacts with a high energy particle, it can produce carbon-14 (6 protons), which is unstable, with a half-life of 5700 or so years. The production of C14 from N14 in the atmosphere is predictable and constant, leading to a state of equilibrium between these two isotopes, and that proportion exists within every living carbon-based life form. When a living thing dies, however, it ceases to interact with its environment, and the unstable C14 gradually decays into stable C12.
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