Lab 3: Atomic Mass of Imaginary Elements

Materials: many small items scale

Procedure: 1. Obtain a sample of an element. 2. Separate the isotopes. Each different item is an isotope. 3. Measure the mass of each isotope. 4. Count the number of pieces of each isotope. 5. Divide the total mass of the isotope but he number of pieces of that isotope. 6. Calculate the percent abundance of each isotope by dividing the number of pieces of the isotope by the total number of pieces of the element and multiplying by 100. 7. Now you have the mass of each isotope and the relative abundance. To calculate the atomic mass, multiply the mass of the isotopes by their relative abundances, and add the totals. 8. Repeat these steps for each element.

Data: Below is a sample chart that you can use for your data and calculations. The sample chart is for the element Candium that is made of isotopes of M+M’s, Skittles, and Reese’s Pieces. Atomic Mass of Candium M+M's Skittles Reese's Pieces Total Total Mass (g) X Number of Pieces Average Mass (g) X % Abundance Atomic Mass (g)

***QUESTIONS ARE ON THE BACK***

Questions: 1. Why are atomic masses on the periodic table not whole numbers? 2. When in your life do you use weighted averages instead of just regular averages? 3. Do isotopes of elements react similarly or differently? Why? 4. The four isotopes of lead and its abundances are: Pb-204, 1.37%; Pb-206, 26.26%; Pb-207,20.82%; and Pb-208, 51.55%. Calculate lead’s approximate atomic mass.