The ratio of hydrogen-1 and hydrogen-2 isotopes in the hydrogen atoms of water molecules in ice cores can be used to provide proxy measurements of historical temperatures. This is possible because this ratio varies throughout nature. The percent abundance of hydrogen-1 varies from 99.9816% to 99.9974% while the percent abundance of hydrogen-2 varies between 0.0026% and 0.00184%. Use the Atomic Weight Calculator to determine the interval of atomic weights which is produced by these variations in isotopic abundances. Compare the atomic weight interval which you obtain with the atomic weight interval for nitrogen given by the IUPAC Periodic Table of the Isotopes.
Enter the isotopic abundances variations of hydrogen into the Atomic Weight Calculator. First, when the abundance of hydrogen-1 is 0.999816 and the abundance of hydrogen-2 is 0.000184, the atomic weight is 1.00801. When the abundance of hydrogen-1 is 0.999974 and the abundance of hydrogen-2 is 0.000026, the atomic weight is 1.007851.
According to the Atomic Weight Calculator, the atomic weight interval for hydrogen is 1.007851 to 1.00801. The atomic weight interval given by the IUPAC Periodic Table of the Isotopes is very similar: 1.00784 to 1.00811.
Your Turn
Chlorine, an element that plays a significant role in the chemistry of the atmosphere, is given an atomic weight interval on the IUPAC Periodic Table of the Isotopes. In nature, the atomic weight of chlorine is between 35.446 and 35.457. Use the Atomic Weight Calculator to determine the percent abundances of chlorine-35 and chlorine-37 which would produce the atomic weight interval given by the Periodic Table of the Isotopes.
Note: The exact values which you have obtained may not be the same as the values in this answer
First, adjust the abundances until the atomic weight is as close as possible to 35.446. The percent abundance of chlorine-35 given by the Learning Tool is about 76.107% and the percent abundance of chlorine-37 is about 23.893%.
Next, adjust the abundances until the atomic weight is as close as possible to 35.457. The percent abundance of chlorine-35 is approximately 75.556% and the percent abundance of chlorine-37 is close to 24.444%.
The percent abundances required to give the atomic weight interval from the IUPAC Periodic Table of the Isotopes is approximately 75.556% to 76.107% for chlorine-35 and 23.893% to 24.444% for chlorine-37.