There are 3 subatomic particles: Neutrons, protons and electrons.
Neutrons: These particles does not carry any charge and are located inside the nucleus.
Protons: These particles carry positive charge and are also located inside the nucleus.
Electrons: These particles carry negative charge and are found around the nucleus in the orbits. If an element looses 1 electron, it will carry positive charge and if an element gains 1 electron, it will carry a negative charge.
Element is identified by its atomic number. Atomic number is defined as the number of protons or number of electrons.
If one, identifies the number of protons, then the element is easily identified. Electrons on the other hand are easy to remove or add, so it is not convenient to use the number of electrons in identifying the element.