The mass spectrum of an element with two naturally occurring isotopes is shown below.What is the best estimate of the element's (average)atomic weight?

Question

Quizplus · Accepted Answer

The atomic weight of an element is the weighted average of the masses of its isotopes. To find the atomic weight, we need to calculate the weighted average of the masses of the two isotopes given in the mass spectrum.

First, we need to calculate the relative abundance of each isotope that contributes to the atomic weight. From the mass spectrum, we can see that the first isotope has a mass of 10 amu and a relative abundance of 80%. The second isotope has a mass of 12 amu and a relative abundance of 20%.

To calculate the atomic weight, we multiply the mass of each isotope by its relative abundance and add the results.

Atomic weight = (10 amu x 0.80) + (12 amu x 0.20) 
Atomic weight = 8 amu + 2.4 amu 
Atomic weight = 10.4 amu

Therefore, the best estimate for the element's atomic weight is 10.8 amu, rounded to one decimal place.

The Mass Spectrum of an Element with Two Naturally Occurring