If bromine atom is available in the form of say, two isotopes ⁷⁹₃₅Br (49.7%) and ⁸¹₃₅Br (50.3%), calculate the average atomic mass of bromine atom.

The atomic number or the proton number of an element is equal to the number of protons in the nucleus of its atom. e.g., Oxygen has 6 protons hence, its atomic no. is 6. The atomic number is denoted by Z.

The mass number of an atom is equal to the number of protons and neutrons in its nucleus.

Thus, we can say that nucleons = number of protons + number of neutrons Example: Protons + Neutrons = Mass number

 Isotopes: Isotopes are atoms of the same element which have different mass numbers but the same atomic numbers

E.g.,  11H, 21H,31H

Now, to calculate the average atomic mass of a bromine atom

= $[79X \frac{49.7}{100}]  + [81X \frac{50.3}{100}]$

= $39.263 + 40.743$

= $80.006 u$

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Updated on: 14-Mar-2023

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