An atom of an element is electrically neutral, with a proton & neutron placed in the nucleus of the atom and electrons moving around the nucleus in orbit. So total positive charge on an atom is equal to the negative charge of an atom therefore atom is electrically neutral.
Coulomb's law state that the force of attraction or repulsion between the two-point charge is directly proportional to the product of the magnitude of the two-point charge and inversely proportional to the square of the distance. It was first observed by the Greek philosopher Thales of Miletus and then in 1785, Charles Augustin de Coulomb derived the actual mathematical relationship between the two points of charge.
First law:
When the two charge particle has the same polarity then repulsion between them and when two charge particle has opposite polarity then they attract each other.
Second Law:
The force of attraction or repulsion between the two-point charge is directly proportional to the product of the magnitude of the two-point charge and inversely proportional to the square of the distance.
Suppose a two-point charge has a magnitude Q1 and Q2 and is separated by distance r therefore electrostatics force is given by
F∝ Q1*Q2/r^2
or, F=Q1*Q2/4πЄr^2
Where Є=Є0*Єr
Є0=8.85*10^12
Єr=1, for air