All the matter we know is made up of molecules. This, in turn, is formed of atoms, which are composed of three types of elementary particles: protons, neutrons and electrons.
Atoms are formed by a nucleus, where protons and neutrons are, and an electrosphere, where electrons remain, in orbit.
Protons and neutrons have roughly equal mass, but electrons have thousands of times less mass. Being m the mass of protons, we can represent the mass of electrons as:
That is, the mass of electrons is approximately 2,000 times smaller than the mass of protons.
We can represent an atom, although out of scale, by:
If we could separate protons, neutrons and electrons from an atom, and toss them toward a magnet, protons would be shifted in one direction, electrons in a direction opposite from proton shifting, and neutrons would not be affected.
This property of each of the particles is called electric charge. Protons are positively charged particles, electrons are negatively charged, and neutrons have a neutral charge.
A proton and an electron have equal absolute values, although they have opposite signs. The charge value of a proton or an electron is called the elemental electric charge and symbolized by and.
The unit of measurement adopted internationally for the measurement of electric charges is the coulomb (C).
The elemental electric charge is the smallest amount of charge found in nature, comparing this value with coulomb, we have the relation:
The coulomb unit is defined based on the knowledge of electric current densities, measured in ampere (A), since their units are interdependent.
A coulomb is defined as the amount of electrical charge that crosses in one second, the cross section of a conductor traversed by a current equal to 1 amp.