posted by Dawn .
The element X has an atomic mass of 12.80
amu. It is known to have two isotopes 12X and 13X. Which of the following is true about the relative abundancies of 12X and 13X?
a) both isotopes occur with the same frequency.
b)12X occurs more frequently than 13X
c)12X occurs less frequently than 13X
d) not enough information
The atomic mass is the weighted average of the masses of all of the isotopes. So if we have a 12.0 and a 13.0 and the average is 12.8 the 13.0 must be there in higher abundance, right?