Final answer:
To calculate the average atomic mass of element Y, multiply the mass of each isotope by its relative abundance and sum the results. For Y, with isotopes Y-14.00 amu and Y-16 amu with relative abundances of 87.9% and 12.1%, respectively, the average atomic mass is 12.31 amu.
Step-by-step explanation:
To calculate the average atomic mass of element Y, we need to multiply the mass of each isotope by its relative abundance and then sum the results.
The average atomic mass (Mavg) can be calculated using the following formula:
Mavg = (M1 x A1) + (M2 x A2)
where M1 and M2 are the masses of the isotopes and A1 and A2 are their relative abundances.
For Y, we have Y-14.00 amu with a relative abundance of 87.9% (or 0.879) and Y-16 amu with a relative abundance of 12.1% (or 0.121). So, the average atomic mass of element Y is:
Mavg = (14.00 amu x 0.879) + (16.00 amu x 0.121) = 12.31 amu.