Question

Silicon has three naturally occurring isotopes. Look at the information given and predict whether the average atomic mass would be closer to Si-28, Si-29, or Si-30. Give reasons for your answer.

A) The average atomic mass would be closer to Si-28 because of its high percent abundance.
B) The average atomic mass would be closer to Si-29 because of its high percent abundance.
C) The average atomic mass would be closer to Si-30 because of its high percent abundance.
D) The average atomic mass would be an equal mix of Si-28, Si-29, and Si-30 due to their percent abundances.

Answer 1

The average atomic mass of silicon is likely to be closer to the mass of Si-28 if its percent abundance is significantly higher than the other isotopes, as it would have a greater influence on the weighted average.

Step-by-step explanation:

The student's question is about predicting the average atomic mass of silicon based on the percent abundances of its naturally occurring isotopes. To calculate the average atomic mass, we would use the percent abundances of the isotopes as weights. For example, if Si-28 has a much higher percent abundance than Si-29 and Si-30, the average atomic mass will be closer to the mass of Si-28.

Therefore, option A would most likely be correct, as it states that the average atomic mass would be closer to Si-28 because of its high percent abundance. To make a precise calculation, one would need the exact abundances of each isotope, but based on this reasoning, the average atomic mass of an element is defined as the weighted average of the masses of its isotopes.