Lab 4: Atomic Mass of Candium Lab

Lab 4

Atomic Mass of Candium Lab

Shiva Senthil

7/18/17

Introduction
The purpose of this lab was to find the average atomic mass of the element "candium." The procedure was to first measure the average mass of the various isotopes, and then using that and the abundance of each isotope to calculate the average atomic mass. The important terms for this lab are: decimal abundance and mass. The decimal abundance is the amount of a certain isotope within the sample of atoms expressed as a decimal rather than a percent. The mass is simply the amount of matter in each isotope.

Data

The following formula is used to calculate the average atomic mass of candium, which has 3 isotopes (regular, Skittle, and pretzel):

Therefore, the values needed for each isotope are its decimal abundance and its mass. 

For the decimal abundance, the simple ratio of number of isotope to the number of atoms in the whole sample was used:

The decimal abundance was found for the three isotopes:

The next step of the calculation is the average mass for each isotope. The average mass per atom for each isotope is calculated with the formula:

Now that both the decimal abundance and the average mass for each isotope have been calculated, the values can be plugged in to the average atomic mass formula:

The calculation turns out to be 0.955 grams as the average atomic mass.

Questions

1. Ask a nearby group what their average atomic mass was. Why would your average atomic mass be different than theirs?

One other group's average atomic mass was 1.10 grams. This difference could have came from the fact that the samples we each used were not exactly the same; the other group may have had more pretzel isotopes, which were much heavier than the more common regular and Skittle isotopes.

2. If larger samples of candium were used, for example if I gave you a whole backpack filled with candium, would the differences between your average atomic mass and others' average atomic masses be bigger or smaller? Defend your answer.

If larger samples were used, the differences between the average atomic masses of different groups would be smaller. This is because a larger sample size is generally more accurate and representative of the population as a whole. For example, if the sample size was only 10 atoms of candium, all 10 atoms for one group might be the pretzel isotope while another group may get 10 regular isotopes, causing the difference between the average masses to be significant. However, if a sample size of thousands of atoms was used, it is much less likely that the number of each isotope would be significantly different than in another group's sample. The demographics of the samples would be much more similar, causing a smaller difference in average atomic mass.

3. If you took any piece of candium from your sample and placed it on the balance, would it have the exact average atomic mass that you calculated? Why or why not?

It would not have the exact average atomic mass because the mass of the different isotopes are different from the average atomic mass. If a regular or Skittle isotope was used, the mass would be slightly less than the average atomic mass. If a pretzel isotope was used, the mass would be much higher than the average atomic mass. The average atomic mass is in between the three isotopes' masses.