Names:_______________________ Adv. Chemistry Average Atomic Mass of “Beanium” Lab Introduction On the periodic table, values for atomic number and atomic mass are given for each element. The atomic number is a whole number that represents the number of protons in the atom. The atomic mass is a decimal number because it represents a weighted average of the masses of the isotopes of each element based on how often each isotope is found in nature. Nuclear chemists have discovered what is believed to be element number 119. The researchers have named this element “Beanium”. There are four naturally occurring isotopes of beanium: beanium-white, beanium spotted, beanium-brown, and beanium-green. Your job is to determine the atomic mass of each individual isotope, the percentage abundance of each isotope, and ultimately the average atomic mass of beanium. One unique property of beanium that should make this determination particularly easy is that beanium atoms are very large, so sorting the isotopes of this element should be accomplished with little difficulty. Purpose To determine the average atomic mass for the fictitious element “beanium”. Pre-Lab Questions & Prediction 1. Chlorine has two isotopes: mass # 35 37 exact mass 34.968852 36.965903 % abundance 75.77 24.23 Using this information, calculate the atomic mass of chlorine. (Show your work!) 2. Prediction: In this lab, you will determine the average mass of all the beans together, and also the average mass of each type of bean based in their abundance. How close do you think these values will be to each other? Equipment balance beaker (100 mL) Materials beans, various types Safety Considerations None for this lab beyond standard lab safety procedures. Names:_______________________ Procedure 1. 2. 3. 4. 5. 6. Obtain a sample of beanium isotopes by scooping up a beaker full of beans from the bean container. Separate the beans by isotope and count them. Record the total number of each type of bean. For each isotope sample of beanium, determine and record its total mass. Determine and record the total mass of your entire sample of beanium. For each isotope, calculate its average mass and percent abundance Calculate the average mass for the total sample using the method from Ch. 5 Data and Calculations White Spotted Brown Green Total Mass of each isotope Number of each isotope Average mass of each Percent abundance of each Clean-up and Disposal 1. Return your beanium sample to the bean container. DO NOT LEAVE ANY BEANS IN THE SINK OR AT YOUR LAB STATION. 2. Wash your hands before leaving the lab. Questions 1. For all the rows except average mass the “total” column could be found by adding the numbers across the row. It is an exception because it doesn’t take into account the different abundances of the different isotopes. Compare the average you found correctly in step 6 to an average mass found by dividing the total mass by the total number. 2. Compare your average mass of beanium with that of two other groups. How does your average mass compare to theirs? Why do you think this happened? 3. If you were to do this lab over again, what would be more helpful – a more precise scale (i.e., 0.001 precision instead of the 0.01 we used) or a larger sample of beans? Why? 4. Neon-20 has a mass of 19.9924 amu, neon-21 has a mass of 20.9940 amu, and neon-22 has a mass of 21.9914 amu. The relative abundance of Ne-20 is 90.92%, while Ne-21 is 0.257% and Ne-22 is 8.82%. Using the same techniques that you used in this lab, calculate the average atomic mass for neon. How does this compare to the value for neon found on the periodic table?