Lab #1: The Atomic Mass of Beanium

The Atomic Mass of Beanium

Scientific Question

How is the atomic mass calculated for an element on the Periodic Table?

Background Information

One of the greatest achievements for a chemist is to discover a new element or learn more information about an existing element. You are about to undertake an experiment to ascertain the atomic mass of the recently discovered element, beanium. Research has verified the existence of three isotopes of beanium that will be called lima-beanium, kidney-beanium, and pinto-beanium. These isotopes are found in nature in the same percent abundance as in the sample you are provided. It is your task to calculate:

  1. The average mass of each of the isotopes,
  2. The percent abundance of each of the three isotopes, and
  3. The “bean atomic mass”

Remember, an atomic mass is the weighted average of all of the isotopes for a particular element, and can be determined using this formula:

Atomic Mass = Σ[(Percent Abundance) x (Mass of Isotope)]

Safety Alerts

  • Do not eat any of the lab supplies because they can be contaminated with other chemical residues that were left of the balances or lab tables.

Pre-Lab Assignment

  1. Define the term, isotope.
  2. Create 2 different graphs to represent the make-up of a sample of magnesium given the information below. Which graph is better and why?

Isotope / Percent Abundance
magnesium-24 / 79 %
magnesium-25 / 10 %
magnesium-26 / 11 %

Procedure

  1. Count all of the lima beans, all of the kidney beans, and all of the pinto beans. Record these numbers in the data table provided.
  2. Measure the mass of all of the lima beans, all of the kidney beans, and all of the pinto beans. Use the dish provided for you at the balance. Remember to zero your scale before massing your beans.

Data

Isotope / Number of the Isotope in Sample / Total Mass of Isotope
lima-beanium
kidney-beanium
pinto-beanium

Results

Calculations

For the first two calculations, show one set of sample calculations (what you type in your calculator)and include units when appropriate. For the other calculations, record your final answers in the table below.

  1. Determine the average mass of each isotope (bean) in grams/bean.
  1. Calculate the percent abundance for each isotope (bean).
Sample Calculations / Final Answer
Average Mass / lima-beanium
kidney-beanium
pinto-beanium
Percent Abundance / lima-beanium
kidney-beanium
pinto-beanium
  1. Using the information from the table above, calculate the atomic mass of beanium. Show all work.

Atomic Mass = Σ [ (Percent Abundance) x (Mass of Isotope) ]

Graph

  1. Create a graph to represent the percent abundance of the three isotopes of beanium.

Analysis Questions

  1. What are the chances that you would find a bean with the exact same mass as your atomic mass? Explain your reasoning.
  2. A student opted to take the mass of a single bean and record that has the average mass of the isotope. How do you think this affected the accuracy of the atomic mass calculation?

Conclusion

Explain how you calculated the mass of your beanium sample. In your explanation, include at least one way that your data collection process may differ from the data collection for an atomic mass of a real element.

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