Hey there!
Potassium has 19 protons.
If this potassium atom has an atomic mass of 41, that means the sum of protons and neutrons is 41.
So, the following must be true:
p + n = 41
p = 19
Which makes this true:
19 + n = 41
Subtract 19 from each side to solve for n, the number of neutrons.
19 - 19 + n = 41 - 19
n = 22
A potassium atom that has an atomic mass of 41 has 22 neutrons.
Hope this helps!
