Question

Three isotopes of an element have the mass numbers A, A+1. And A+2. if they are
present in 3:2:1 ratio, what is the average atomic mass of the element.​

Answer 1

Answer:

a/2+(a+1)/3+(a+2)/6= a+1/2 ans. or. (2a+1)/2

Answer 2

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Average atomic mass of the element = A + 0.67

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According to the question,

3:2:1 is the relative abundances of three isotopes having mass numbers - A, (A + 1) & (A + 2).

$\therefore$ Average/Mean atomic mass =

$\bold{\frac{3\times{}A+2\times{}(A+1)+1\times{}(A+2)}{3+2+1}=\frac{3A+2A+A+2+2}{6}=\frac{6A+4}{6}=A+0.67}$