To calculate the average mass of the element, we take the summation of the product of the isotope and the percent abundance. In this case, the equation becomes 186.207=187*0.626+185*x where x is the percent abundance of 185. The answer is 0.374 or 37.4%. This can also be obtained by 100%-62.6%= 37.4%.
The answer would be 8 just took the test
0.500 moles is roughly .5*6.022*10^23=3.011*10^23 atoms. This is independent of STP.
Answer; +3
Example Ca3(PO4)2
