Q. 4.40 - An Introduction to General, Organic, and Biological Chemistry

Question

Two isotopes of rubidium occur naturally, ${}_{37}{}^{85}Rb$ and ${}_{37}{}^{87}Rb$. Which isotope of rubidium is more abundant?

Step-by-Step Solution

Answer

The isotope of rubidium which is more abundant is ${}_{37}{}^{85}Rb$.

Step 1: Given information

We need to find that out of ${}_{37}{}^{85}Rb$ and ${}_{37}{}^{87}Rb$which is more abundant.

Step 2: Explanation

The atomic mass of an element on the periodic table is used to find the most abundant isotope. The atomic mass of rubidium is $85.468 amu$, as can be shown. Although no rubidium atom has that mass, it is the average mass of a rubidium sample.

When comparing the atomic masses of ${}_{37}{}^{85}Rb$ and ${}_{37}{}^{87}Rb$, we can see that the atomic mass number on the periodic table is closer to that of ${}_{37}{}^{85}Rb$.

We can deduce that ${}_{37}{}^{85}Rb$ is more plentiful.