Centripetal force
Within nucleus electron revolves surrounding nucleus is not collapse even, not go far from nucleus.
It is nothing but a result of electrostatic force. Electrostatic force is a combination of two forces opposite direction. These are centripetal force electron direction toward centre and centrifugal force which is directed opposite of centre.
According to Rutherford atomic model, both forces are equal and opposite direction within an electron.
Centripetal force Directed toward the centre of atom.
Any forces directed toward centre is centripetal force.
Centripetal force are always found in circularmotion. When any object moves circularly the centripetal force act towards centre of the circular path along with radius of the circle.
The force is always orthogonal and fixed to the centre of the curvature.
Gravity is a best example of centripetal force. Issac Newton says that it always drawn object. In Newtonian classical mechanics, Centripetal force causes due to orbits of astronomical objects.