Atomic structure

All matter is composed of atoms which contain electrons, protons, and neutrons. Electrons are in the empty space. While protons and neutrons are in the nucleus.

Nucleus- The nucleus Is the center of an atom which contains protons and neutrons.

Protons- protons are subatomic particles that make up the nucleus of an atom. The proton has a positive electric charge and is part of the Byron family. Since  it has three colored quarks, 2 up quarks and one down one.
Number of Protons = Atomic Number

Neutrons- neutrons also make up the nucleus and are subatomic particles. The neutron has a neutral charge. Neutrons are also made up of three quarks. However, the neutron had two down quarks and one up quark unlike the proton.
Number of Neutrons = Mass Number - Atomic Number

Electrons- Electrons are subatomic particles that orbit the nucleus and have a negative electric charge. Electrons are held there by an electromagnetic force.
Number of Electrons = Number of Protons = Atomic Number

Example- Helium  

Protons=2                                                                                                                                                   Neutrons- 4.003-2= 2.003                                                                                                                          Electrons=2

The history of the atom- In the early years people did not believe or even know of atoms. The first to come upon the idea that matter was not infinitely divisible was a philosopher named Democritus. Since he could not back up why, his idea was shunned. That theory was discard but reopened in the 18th century. John Dalton finally figured it out in the 19th century and said all matter is composed of extremely small particles called atoms. Thats how atoms came to be.