A dash of physics the forces acting between particles carrying electric charge

2 A dash of physics the forces acting between particles carrying electric charge 

The electric charge on a particle may be positive or negative, and is measured in coulombs. Thus the charge on an electron is 

Chemists often use the elementary charge (e) as an atomic unit (a. u.) of charge. 

The force acting between two particles with electric charges Q and Q2 is given by  

If Q and are given in coulombs, and the distance in meters, the force will be given in newtons (1 newton = 1 J m ). If Q, and Q2 have the same sign, F will be positive, indicating that the particles repel each other and that the direction of the force is such as to tend to increase r. If Qi and Q2 have opposite signs, F will be negative, the particles attract one another and the direction of the force tends to decrease the distance between them. 

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