Question

Bromine occurs in nature mainly in the form of two isotopes if the abundance of 1.) ^79 Br isotope is (49.7) percent. 35. 2.) and that of ^81 Br isotope is (50.3) percent.35 calculate the average mass of bromine
for class 9th chemistry structure of the atom

Answer 1

Average atomic mass of an element is calculated by taking the weighted average of the atomic masses of stable Isotopes.
In this case , as we know Bromine has two stable Isotopes, Bromine-79 and Bromine -81.
The isotope with mass 79 is present in 49.7% and isotope with mass 81 is present in 50.3% in nature.
Therefore Average atomic mass of bromine is:
= ( 79x49.7/100) +(81x50.3/100)
=(79x0.497) + (81×0.503)
=39.264 + 50.743
=80.006u