Chemistry: How many Neutrons?

M = P + N

That equation can be used to find the number neutrons in an atom if you only know the atomic mass (the mass of the atom) and the number of protons.

The equations means:

M (mass) = P (protons) + N (neutrons)

So if you add the number of protons and Neutrons you get most of the mass.

The number of protons and electron are the same.

Electrons take up very little mass they are almost 2000 times less (1836 time less to be exact) mass than protons or neurons.

M = P + N can also be used to find the number of neutrons for example potassium has an atomic mass of 39.1 and 19 protons.

39.1 - 19 = 20.1 There are about 20 neutrons in a potassium atom.

Chemistry for Dummies
www.eskom.co.za