90.92% of the atoms have a mass of 19.988 u, 0.26% of the atoms have a mass of 20.983 u and 8.82% of atoms have a mass of 21.978 u. Calculate the average atomic mass of this element
0.9092(19.988) + (0.0026*20.983) + (0.0882*21.978) = ??
To calculate the average atomic mass of the element, you need to multiply the mass of each isotope by its abundance (expressed as a decimal), and then sum the results.
Let's start by converting the percentages to decimal values:
For the isotope with a mass of 19.988 u: abundance = 90.92% = 0.9092
For the isotope with a mass of 20.983 u: abundance = 0.26% = 0.0026
For the isotope with a mass of 21.978 u: abundance = 8.82% = 0.0882
Now let's calculate the weighted average atomic mass:
(19.988 u * 0.9092) + (20.983 u * 0.0026) + (21.978 u * 0.0882)
= 18.1475 u + 0.0544178 u + 1.9405036 u
= 20.1424 u
Therefore, the average atomic mass of this element is approximately 20.1424 unified atomic mass units (u).