Custom Search
Atomic Mass "An atomic weight (relative atomic mass) of an element from a specified source is the ratio of the average mass per atom of the element to 1/12 of the mass of 12C" in its nuclear and electronic ground state. A sample of any element consists of one or more isotopes of that element. Each isotope is a different weight. The relative amounts of each isotope for any element represents the isotope distribution for that element. The atomic weight is the average of the isotope weights weighted for the isotope distribution and expressed on the 12C scale as mentioned above. Atomic Mass Calculations
The equation continues on[….] based on the number of isotopes in the problem.
If you look in the periodic table you will be able to check that our answer is correct!
Determining the percent abundance of each isotope from atomic mass. Copper exists as two isotopes: 63Cu (62.9298 amu) and 65Cu (64.9278 amu). What are the percent abundances of the isotopes?
AP Example 2 The atomic mass of lithium is 6.94, the naturally occurring isotopes are 6Li = 6.015121 amu, and 7Li = 7.016003 amu. Determine the percent abundance of each isotope. 6.94 =[(% 6Li)(6.015121)] + [(%7Li)(7.016003)] Since I don’t know what the percentage are, I will have to use variables. 100% of Lithium is determined by these two naturally occurring isotopes. We will let 6Li = x and 7 Li = 1-x; we use 1 – x instead of 100 – x because the small number is easier to work with. (in other words we reduced 100% to decimal form 1.00)
|