Answer:
Atomic mass of element = 38.25 amu
Explanation:
Let X-39 abundance = 75% and X-36 abundance = 25%
Atomic Mass of element = ∑ wt average contributions of each isotope ...
Wt Avg Contribution = fractional abundance x isotopic mass.
Isotope Isotopic Mass (amu) Fractional Abundance Wt Avg Contbn
X-39 39.00 0.75 29.25 amu
X-36 36.00 0.25 9.00 amu
∑ Wt Avg Contributions = 29.25 amu + 9.00 amu = 38.25 amu
=> Atomic mass of element = 38.25 amu
