In each of the following pairs, which isotope would you expect to be more common in nature? Briefly explain your answer.

Question

In each of the following pairs, which isotope would you expect to be more common in nature? Briefly explain your answer.

a. palladium-106 or palladium-113

b. xenon-128 or cesium-128

Answer 1

Remember that an Isotope is the same element's atom with a different atomic mass (because Neutrons!), and put that together with the knowledge that the Atomic Mass from the periodic table is the Average of all isotopes, then we know that the isotope with it's mass closest to the Average Atomic Mass on the periodic table will be the one that occurs most.

For example: Carbon has many isotopes, such as Carbon-12, Carbon-13 and Carbon-14. The Average Atomic Mass on the periodic table for Carbon is 12.011, so Carbon-12 is the isotope that occurs most.