The Basic Structure Of Atom

While we are on earth, the terms MASS and WEIGHT reflect the same thing.
It's been said that if you want to lose weight, go to the moon.
For our purposes in this article, the terms MASS and WEIGHT will be used interchangeably, since we are on earth.
There are a little more than 100 known elements, and they are listed in the Periodic Table.
For example, water is made up of two ELEMENTS, Hydrogen and Oxygen.

All atoms have a NUCLEUS, with ELECTRONS zooming around it.

The NUCLEUS contains most of the MASS, or WEIGHT, of the atom.
The number of PROTONS in each type of atom is always the same.
Helium atoms always have two PROTONS.
All Nitrogen atoms have seven PROTONS, etc.
This number is called the ATOMIC NUMBER.
Helium's ATOMIC NUMBER is 2.
Nitrogen's ATOMIC NUMBER is 7, etc.
Helium atoms sometimes have 2 NEUTRONS and others have 3 NEUTRONS.
Nitrogen atoms sometimes have 7 NEUTRONS and others have 8 NEUTRONS, etc.

If you add up the number of PROTONS and the calculated average of NEUTRONS in an atom, you will get the ATOMIC MASS, or ATOMIC WEIGHT, or MASS NUMBER.
If you look on a Periodic Table, you will see that the MASS NUMBER of Helium is 4.
The ATOMIC WEIGHT of Nitrogen is 14.
The reason they are not whole numbers is because of what we discussed in the previous paragraph the number of NEUTRONS is a calculated average.
NEUTRONS have no electrical charge, they are neutral.
In an electrically neutral atom, the number of ELECTRONS and the number of PROTONS are the same, balancing it out to make it neutral.
ELECTRONS zoom around outside the nucleus in orbitals and take part in chemical reactions.
They do not take part in chemical reactions.