Question

The species $$^{27}\mathrm{Al}$$, $$^{80}\mathrm{Br}^{-}$$ and $$^{201}\mathrm{Hg}^{2+}$$ have 13, 35 and 80 protons, respectively. How many electrons and neutrons do they have?

Answer 1

For $$^{27}\mathrm{Al}$$:

protons = 13

electrons = 13

neutrons = 27 − 13 = 14. 

For $$^{80}\mathrm{Br}^{-}$$:

protons = 35

electrons = 35 + 1 = 36

neutrons = 80 − 35 = 45. 

For $$^{201}\mathrm{Hg}^{2+}$$:

protons = 80

electrons = 80 − 2 = 78

neutrons = 201 − 80 = 121