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That is done to calculate the weighted average.

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Q: Why is each isotope's mass multiplied by the isotope's percent abundance?
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Why do elements which exists as isotopes have fractional atomic mass?

Each isotope of an element has a different Atomic Mass, so an average is taken of all the isotopes, but the average is weighted because the natural abundance (%) of each isotope is factored in. If hydrogen-1 is much more abundant than deuterium and tritium, then the weighted average will be closer to 1 than 2 or 3 but not a whole number. The following equation shows how percent abundance factors into the weighted average. (atomic mass A)(X% abundance) + (atomic mass B)(Y% abundance)...=(weighted average of all isotopes of the element)(100% abundance)


How do you calculate the atomic mass of an element with different isotopes?

To calculate average atomic mass from different isotopes of an element, we take into account the relative atomic masses of isotopes and their relative abundance on Earth. The following formula is used to calculate the needful : atomic mass = mass of isotope x percent abundance + mass of isotope x percent abundance / 100 (whole expression divided by 100)


Why do isotopes change the atomic mass of an element?

Isotopes of a element are simply versions of that same element with different count of neutron, with that in mind they take all of the isotopes of a specific element and average them together taking in account the percent abundance of each so the most common isotope is the one on the periodic table.


How does the atomic mass of carbon show that it is an isotopes?

If your asking "how does the mass show there are isotopes", then the answer is this: Isotopes are found by using a mass spectrometer, and the abundance (percent amount) of each isotope is determined. Using this percent of abundance, the AVERAGE mass is reported on the periodic table. For example, if carbon 12 had mass of 12 and carbon 13 had mass of 13, but the percent abundance of 12 was 99% and the abundance of 13 was 1%, then the atomac mass would be 12*.99+13*.01=12.01 You can tell it has isotopes by seeing that the mass is a decimal and not a whole number. It is harder to tell with carbon, because it's only off by .01, but looking at chlorine it is more clear. Most isotope weights are very close to being whole numbers, like Cl35 mass is 34.98 and Cl37 is 36.97. But looking at Cl atomic weight, it is 35.45; the .45 tells you it is a average because the value lies between the whole numbers as a decimal. Cl is 35.45, which is an average of 35 and 37 that's 76% and 24% abundance respectively.


How much effect do high percent abundance isotopes have on the average atomic mass of an element?

This entirely depends on the percentage of the different isotopes present. This is typically determined through mass spectrometry. After the percentages of the different isotopes are known, one times the percentage of each isotope by its relative atomic mass, then add this all together. After dividing this by 100, you will have attained the average atomic mass of a naturally ocurring element.

Related questions

If an element has 3 isotopes with known masses what other information is needed to find the average atomic mass of the element?

You would also need to know the abundance of each of the isotopes, i.e., how much percent of each you will typically encounter.


What is the result when you total the individual percent abundance of isotopes of a given element?

How do you calculate percent abundance of an isotope?You find the isotope number and then you calculate that into a fraction and then turn the fraction into a percentage and divide it by the atomic number then times it by the mass and turn that answer into a percent and voila, there you have it.


Why do elements which exists as isotopes have fractional atomic mass?

Each isotope of an element has a different Atomic Mass, so an average is taken of all the isotopes, but the average is weighted because the natural abundance (%) of each isotope is factored in. If hydrogen-1 is much more abundant than deuterium and tritium, then the weighted average will be closer to 1 than 2 or 3 but not a whole number. The following equation shows how percent abundance factors into the weighted average. (atomic mass A)(X% abundance) + (atomic mass B)(Y% abundance)...=(weighted average of all isotopes of the element)(100% abundance)


When the masses of all naturally occurring isotopes of a particular element are averaged the result of the elements?

When the mathematical products of the mass of each naturally occurring isotope of a particular element, each mass being multiplied by the natural abundance fraction* of the particular isotope, are added, the result is called the element's atomic weight or, if the masses are expressed in grams per Avogadro's Number of atoms, the gram atomic mass._____________________________*The abundance fraction equals exactly 0.01 times the percent abundance of the isotope.


When masses of all naturally occurring isotopes of a particular element are averaged the result is called the elements?

When the mathematical products of the mass of each naturally occurring isotope of a particular element, each mass being multiplied by the natural abundance fraction* of the particular isotope, are added, the result is called the element's atomic weight or, if the masses are expressed in grams per Avogadro's Number of atoms, the gram atomic mass._____________________________*The abundance fraction equals exactly 0.01 times the percent abundance of the isotope.


When the masses are all naturally occurring isotopes of a particular elements are averaged the result is called a element?

When the mathematical products of the mass of each naturally occurring isotope of a particular element, each mass being multiplied by the natural abundance fraction* of the particular isotope, are added, the result is called the element's atomic weight or, if the masses are expressed in grams per Avogadro's Number of atoms, the gram atomic mass._____________________________*The abundance fraction equals exactly 0.01 times the percent abundance of the isotope.


What are the percent natural abundances of the two isotopes Ru-85 and Ru-87?

Their percent natural abundances are Ru-85 (72. 2 percent) and Ru-87 (27. 8 percent). Ru-85 and Ru-87 are the only naturally occurring isotopes of Rubidium out of its 35 known isotopes.


How do you calculate the atomic mass of an element with different isotopes?

To calculate average atomic mass from different isotopes of an element, we take into account the relative atomic masses of isotopes and their relative abundance on Earth. The following formula is used to calculate the needful : atomic mass = mass of isotope x percent abundance + mass of isotope x percent abundance / 100 (whole expression divided by 100)


Why don't we use normal mean to average all of the isotopes of each element?

Because their abundance is not the same.


What is percent abundance?

Take percent abundance times atomic mass for each isotope then add all up for average atomic mass.


The relative abundance of each isotope of an element determines its?

The relative abundance of each isotope of an element is used to determine its atomic mass. This is the weighted average of all naturally occurring isotopes.


Why do isotopes change the atomic mass of an element?

Isotopes of a element are simply versions of that same element with different count of neutron, with that in mind they take all of the isotopes of a specific element and average them together taking in account the percent abundance of each so the most common isotope is the one on the periodic table.