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atomic weight are average atomic masses, the sum of the mass of each naturally occurring isotope of an element times its fractional abundance.
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All elements exist as isotopes in nature. This means that carbon has 6 protons, but some varieties have 6 neutrons and some may have 8. This would be denoted as carbon - 12 and carbon -14
A fractional abundance simply means, what is the mixture of these isotopes in nature. or the carbon example above, approx. 99% is the carbon -12 variety and less than 1 % is carbon-14.
When they are averaged together, based on this relative presence in nature, you get an average Atomic Mass of 12.011
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How are pennies similar to isotopes?
how do you find the fractional abundance of an isotope?
The atomic mass of an atom is equal to the sum of the numbers of what?
The mass number of an atom is the average of all it's isotopes in ratio to how often an isotope occurs naturally (abundance). An isotope is a variant of an element that has a different number of neutrons, therefore causing the atom to have a different mass. The percent abundance of an isotope is converted to a fraction, and multiplied by the mass of the isotope. Then all the factional masses of different isotopes are added together. Atomic mass = (mass isotope 1)x(fractional natural abundance of isotope 1) + (mass isotope 2)x(fractional natural abundance of isotope 2) + (mass isotope 3)x(fractional natural abundance of isotope 3) For example: Hydrogen has 3 naturally occurring isotopes: Protium - Abundance - 99.985% (.99985) Mass - 1.0078 Deuterium - Abundance - .015% (.00015) Mass - 2.014 Tritium - Abundance - 0% (.000) Mass - 3.016 Atomic mass number of Hyrdogen = (.99985)(1.0078) + (.00015)(2.014) + (.000)(3.016) = 1.00795 Go look up the mass number of Hydrogen on the periodic table and it says 1.008
What is the fraction in calculating the average atomic weight of an element?
The fraction represents the abundance of each isotope of the element. It is calculated by multiplying the fractional abundance of each isotope by its atomic mass, then summing these products to obtain the average atomic weight.
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)
Why electrolysis can be separate by fractional distillation?
Electrolysis is a process, fractional distillation another.
