Answer:
The isotope that is not commonly used for dating objects is Phosphorous-32.
Step-by-step explanation:
Phosphorous-32 is most commonly found in organic molecules and is mostly used in biochemistry, molecular biology, and medicine. It can be used to track phosphorylated molecules.
Carbon 14 is an isotope that is used while determining and finding the age of old and ancient objects. Meanwhile, Potassium 40 is an isotope that is used in determining the age of minerals and rocks. Also, Rubidium 87 is a rubidium element isotope that is used for determining and dating the age of rocks. Only Phosphorous 32 is not used for dating objects out of the four isotopes.