Attraction & repulsion of atom:
It can be observed, that if two negatively charged bodies are brought together, there is a force of repulsion between them. Similarly if two positively charged bodies are brought together there is a force of repulsion. However, if a positively charged body is brought close to a negatively charged body, they attract each other. Hence:
Like Charges Repel, Unlike Charges Attract.
The force of attraction or repulsion is governed by an inverse square lawUNIT OF CHARGE
The charge on an electron is very small, therefore a more practical unit of charge called a Coulomb, has been chosen:
One Coulomb = 6.29 x 10^{18} electrons