Question

Calculate the number of electron proton and neutron in 40k+

Answer 1

Here, 

Mass Number of K+ = 40

Electron number is = 19 - 1 = 18

Proton number = 19

We know,
Mass Number = Proton number + Neutron number
Thus, Neutron number = Mass number - Proton number
Hence, N = 40 - 19 = 21

So, we have, Proton number = 19
Electron number = 18
Neutron number = 21