Beanium Isotope Lab
Purpose: The purpose of this lab is to practice calculating atomic mass.
Introduction: Look at your periodic table. What is the EXACT atomic mass of Chlorine?
______
Remember that
atomic mass is the SUM of protons and neutrons. So why is the atomic mass a decimal? To answer this question, you
will receive a container of beans “atoms”. All of the beans are atoms of the same element, but they are different colors
and sizes (masses). Each bean represents an isotope of the element Beanium (Bn). Your job is to calculate the atomic
mass of Bn so that we can add it to the periodic table. Good Luck.
SAFTEY: 1) Do not EAT the beans 2) Do not throw the beans 3) Do not crush the beans – don’t “MESS” with the beans.
Pre-Lab Questions:
1) There are many beans in your container. Each bean represents an _________________________.
2) There are three kinds of beans in your container, each kind represents a different _________________.
3) What is an isotope?
4) What is the subatomic difference between the kinds of “atoms” (beans) in your container?
5) Are atoms really big enough to see with the naked eye?
Procedures:
1)
2)
3)
4)
Separate the beans into groups according to their color (type).
Count the number of each isotope (bean color/type). Record this number in the data table.
Calculate the TOTAL NUMBER of isotopes (white + red + black)
Pretend that you put one atom of each type of bean on the balance. You find the mass of each white isotope
(bean) to be 5 AMU, each black isotope (bean) to be 20 AMU, and the red isotope (bean) to be 49 AMU.
5) Calculate the relative abundance of each isotope (Number of Isotopes / TOTAL NUMBER), and record it in the
data table.
6) Calculate the relative mass of each isotope (Mass number (AMU) * Relative Abundance)
7) Calculate the Weighted Average Mass of Beanium by adding up the relative masses. This weighted average is
the Atomic Mass of Beanium. (Also sometimes called the Atomic Weight)
Isotope Type
Number of
Isotopes
White
Black
Red
TOTAL NUMBER ___________
Mass Number of
Isotope (AMU)
5
20
49
Relative Abundance
of each isotope
Relative Mass of
each isotope
Weighted Average Mass ___________
of Beanium
(Atomic Mass)
Discussion Questions
1) Which isotope is the least abundant?
2) Which isotope is the most abundant?
3) Explain how the atoms of one element differ from those of another element.
4) Explain how the atoms of one isotope differ from those of other isotopes of the same element
5) TRUE or FALSE – the Atomic mass is always a decimal.
6) Pretend that the atomic number of Beanium is 4 and the symbol is Bn. Write the symbols for the three isotopes
of Beanium . Example: Carbon-14 has an atomic number of 6. The symbol of this isotope is 146 C
7) Chlorine has two isotopes. Chlorine-35 makes up 75.8% of naturally-occurring chlorine. Chlorine-37 makes up
24.2%.
a.
Compare and contrast the atomic structure of the two chlorine isotopes.
b.
Calculate the average atomic mass of chlorine. SHOW YOUR WORK!