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?
To determine the relative abundances of isotopes 12X and 13X, we need to consider the atomic mass given and the natural abundance of isotopes.
First, we need to understand what atomic mass means. Atomic mass is the weighted average mass of all the naturally occurring isotopes of an element. It takes into account both the mass and abundance of each isotope.
In this case, element X has an atomic mass of 12.80 amu. We know that there are two isotopes, 12X and 13X.
To determine the relative abundances, we need to compare the atomic mass with the masses of the isotopes. Since the atomic mass is closer to the mass of 13X (13 amu) than to the mass of 12X (12 amu), it suggests that the isotope 13X is more abundant.
Therefore, the answer is c) 12X occurs less frequently than 13X.