How many grams of isotope nitrogen-13 will be left after 20 minutes if you start with a mass of 40 gms (half life = 10 minutes)?

If you start with a mass of 40 grams of isotope nitrogen-13 (half-life = 10 minutes), after 20 minutes there will be 10 grams left. Nitrogen present naturally is made up of nitrogen 15 (the least common) and nitrogen 14 (the most common) which are very stable isotopes.

Nitrogen also is made up of unstable radioactive isotopes- fourteen of them to be exact. The half-lives of these different isotopes are very important to track their level of decay since different isotopes will have different rates of decay.

The answer to this is 10. The half life of the isotope nitrogen 13 will be lessened by half two times. This means that in the beginning, it will be lessened into half which is 20. Then it will be lessened to another half which is 10. This is why the answer to this question is 10.

An isotope is usually two or more forms of the same element that in this case is nitrogen that has the same number of protons but with different number of electrons. The isotope usually has differences with their atomic mass but their chemical properties are the same.