# The Effect of Different Isotopes on Atomic Mass (Chemistry Lab)

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The Effect of Different Isotopes on Atomic Mass
Introduction:
An isotope is a variation of an atom that already exists. An isotope is different from an atom because of the number of neutrons in its nucleus. Finding the amount of neutrons in an atom can be calculated by subtracting the atomic number of a specific atom from its atomic mass. When looking at the periodic table, the atomic mass in the top left corner of every box is a decimal. The mass is in decimal format because the number listed is an average of that atom, plus all of its isotopes. Isotopes have different masses because neutrons weigh 1 amu where as an electrons weight would be negligible. The experiment described below shows how including all isotopes of one element effect the average atomic mass of the element. Materials:

1. Calculator
2. Whitium sample
3. Brownium sample
4. Blackium sample
5. 3 plastic cups
6. Electronic balance
7. Data table

Procedure:
1. Separate the whitium, brownium, and blackium samples from each other. 2. Find the mass of 1 cup with the electronic balance.
3. Put the different samples in separate cups and count the number of beans in each cup; write those numbers in the data table. 4. Find the total number of beans.
5. Find the mass of each cup of beans (using the electronic balance) and subtract the mass of the cup. Write these numbers in the data table. 6. Divide the mass of each sample by its respective amount of beans to find the average mass of one bean. Write these numbers in the data table. 7. Divide the number of beans from 1 sample by the total number of beans to find the percent of the total that that particular isotope takes up. Do this for each of the samples. Record these numbers in the data table. 8. To find the average atomic mass of beanium, use the following formula:

percent of balckium atoms∙average mass of blackium
percent of brownium atoms ∙average mass of brownium
+percent of...