Atomic Structure

Atoms are the smallest units of an element. The atoms of a certain element are different from those of another element.

The atom is made up of 3 subatomic particles : Proton, Neutron, Electron

A proton is positively charged (1+)
An electron is negatively charged (1-)
A neutron is neutral (0)

More about protons:

The number of protons in an atom is known as "proton number". The proton number can be found in the periodic table. It is the number found at the bottom of the element symbol. Another term used for proton number is "atomic number". They both mean the same thing.

Nucleon number:
Nucleon numbers are the sum of the number of protons and neutrons. Nucleon number is also known as "mass number".
*Note! : Nucleon and neutron are different!!!!

Electrons
The number of electrons is the same as the number of protons in an atom. Electrons can be gained or lost.

When an atom loses one or more electrons, it becomes a positively charged (1+) particle, otherwise known as cation.
When an atom gains one or more electrons, it becomes a negatively charged (1-) particle, otherwise known as anion.
*Note: This is because the number of protons and electrons are no longer evenly balanced. Remember that a proton is positively charged while an electron is negatively charged.