How to Calculate Isotope Abundance
Isotope is a chemistry term used to describe the elements of the periodic table. Specifically, it describes the difference between two atoms that have the same number of protons but a different number of neutrons. When this occurs, the two are said to be isotopes of one another. Isotope abundance is an expression of how frequently the various isotope arrangements of a given element actually occur.
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Instructions
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Gather the necessary information. You need to know the average atomic mass of the element in question. You will also need to know the atomic mass of each individual isotope for which you want to calculate the abundance percentage.
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Enter the information into the formula (b)x + (1-x)(c)=a, where "x" represents the unknown abundance, "a" represents the average atomic mass of the element, "b" represents the atomic mass of the first isotope, and "c" represents the atomic mass of the second isotope. For example, let's say that we are dealing with an element that has an average atomic mass of 5. Let's also assume that this element has two potential isotopes with atomic masses of 6 and 4 respectively. After plugging these numbers into the formula we would have (6)x + (1-x)(4)=5.
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Solve for "x". Using our example, this would give us (6)x + (1-x)(4)=5 --> 6x + 4 - 4x=5 --> 2x + 4=5 --> 2x=1 --> x=0.5.
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Subtract "x" from the number 1. We will call the result of this subtraction "y". Using our example, this would give us 1 - 0.5 = y --> y=0.5
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Multiply "x" by 100. The result is the abundance percentage of the first isotope. Using our example, this would give us 0.5 x 100 = 50%.
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Multiply "y" by 100. The result is the abundance percentage of the second isotope. Using our example, this would give us 0.5 x 100 = 50%.
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Tips & Warnings
For a table outlining the official isotope abundances of each element, please refer to the resources section.
References
Resources
- Photo Credit atom_topaz image by Sergey Tokarev from Fotolia.com
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Comments
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shasco
Oct 11, 2010
I have a question about how to calculate this if you get this given : W-182 ??? in 181,948206 u W-183 ??? in 182,950224 u W-184(30,64%) in 183,950933 u W-186(28,43%) in 185,954362 u Now calulate the % of W-182 and W-183 how should I do that , with only this information given?
