Question

an element has three naturally occurring isotopes. the isotope with a mass of 88 occurs 95% of the time, the isotope with a mass of 87 occurs 3% of the time, and the isotope with a mass of 86 occurs 2% of the time. which mass would most likely represent the atomic mass of the element? 87.9 amu 86.7 amu 88.6 amu 87.04 amu

Explanation:

Step1: Convert percentages to decimals

$95\% = 0.95$, $3\%=0.03$, $2\% = 0.02$

Step2: Calculate weighted - average

The atomic mass $A$ is calculated as $A=(88\times0.95)+(87\times0.03)+(86\times0.02)$.
First, $88\times0.95 = 83.6$.
Second, $87\times0.03=2.61$.
Third, $86\times0.02 = 1.72$.
Then $A=83.6 + 2.61+1.72=87.93\approx87.9$ amu.

Answer:

A. 87.9 amu