Strontium (average atomic mass = 87.62) naturally exists as 4 stable isotopes with masses of 84, 86, 87, and 88. Which statement is correct?

Question

Strontium-88 is the most abundant.

Strontium-87 is the most abundant.

All strontium isotopes are equally abundant.

Strontium-86 is the most abundant.

Answer 1

Strontium-88 is the most abundant.

Average atomic masses on the Periodic Table of the Elements are averages based on the abundances (how common) of the different isotopes (versions of the element- same number of protons, but having different numbers of neutrons resulting in different atomic masses). Since the average atomic mass (of 87.62) is closest to the mass of 88, the isotope with the mass of 88 must be most common.