The natural distribution of the isotopes of a hypothetical element is 60.795% at a mass of 281.99481 u,22.122% at a mass of 283.99570 u,and the remainder has a mass of 286.99423 u.Calculate the atomic mass of the element.
A)281.99 u
B)283.29 u
C)284.00 u
D)284.33 u
E)286.99 u

Question

Quizplus · Accepted Answer

The atomic mass of the element can be calculated by taking the weighted average of the masses of its isotopes, based on their natural abundance. The calculation is as follows:$$ \text{Atomic mass} = (0.60795 \times 281.99481) + (0.22122 \times 283.99570) + (0.17083 \times 286.99423) $$$$ \text{Atomic mass} = 171.290 + 62.798 + 49.049 $$$$ \text{Atomic mass} = 283.137 $$Rounded to two decimal places, the atomic mass is 283.29 u.

The Natural Distribution of the Isotopes of a Hypothetical Element