Atomic Structure - Nucleons and Electrons

The name nucleon is the name give to protons and neutrons within the nucleus collectively. So when the amount of protons and neutrons are added together this gives you the total amount of nucleons within the atom. This is also known as the nucleon number or its atomic mass number which is the given the symbol A.


Neutrons are given the symbol of N, and protons are given the symbol Z.

A = N + Z

This equation can be used to calculate the amount of neutrons in an element because each element can only have a set number of protons otherwise it cannot be an atom of that element. Take helium for example if you were to look at a periodic table you would find that it has an atomic (proton) number of 2 and an overall nucleon number of 4 meaning that it has 2 neutrons.

A = N  + Z
 4 = N  +  2
N =  4  -  2
N =  2

To find out how many electrons an atom has all you need is its atomic (proton) number as all elements have no overall charge to them so the amount of electrons is exactly the same as the amount of protons. However ions can be formed which is when an atom has a different number of electrons to the amount of protons. For example helium has 2 protons and 2 electrons in its standard form but it could become positively charged if it were to loose an electron. This is now known as a helium ion which would be written as He⁺ to show that it has become positively charged.