Question

The element loncapium has three isotopes. The first Lc-82 has a mass of 81.2372 amu and makes up 47.36% of a standard sample. The second isotope, Lc-83, has a mass of 82.5759 amu and makes up 38% of a standard sample. The third isotope, Lc-85 has a mass of 84.0536 amu and makes up the remainder of the sample. What is the average atomic mass of this element?

Answer 1

Answer: The average atomic mass of lonacapium 82.1581 amu.

Solution: To calculate average atomic mass of element, we use the formula:

$\text{Average atomic mass}=\sum_{i=1}^n(\text{atomic mass of isoptes})_i\times (\text{percentage abundance})_i$      ....(1)

First isotope, Lc-82

Atomic Mass of Lc-82 isotope=81.2372 amu

Percentage abundance = 47.36%= 0.4736

Second isotope, Lc-83

Atomic Mass of Lc-83 isotope=82.5759 amu

Percentage abundance = 38%= 0.3800

Third isotope, Lc-85

Atomic Mass of Lc-85 isotope =84.0536 amu

Percentage abundance = 100% - 47.36% -38% = 14.64%= 0.1464

Putting the values in equation 1.

$\text{Average atomic mass}=(81.2372\times 0.4736)(82.5759\times 0.38)(84.0536)\times 0.1464)amu$

Average atomic mass of Loncapium = 82.1581 amu