Question

26 if an element has 3 common isotopes and the abundance of two of the ions is 50% and 20%, what is the abundance of the 3rd ion? a 36% b 25% c 30% d 100%

Explanation:

Step1: Recall isotope abundance rule

The sum of abundances of all isotopes of an element is 100%.

Step2: Set up the equation

Let the abundance of the third isotope be $x$. Then $50\%+20\% + x=100\%$.

Step3: Solve for x

$x = 100\%-(50\% + 20\%)=30\%$.

Answer:

C. 30%