@ nirmohi
Electrons do revolve , but the orbits are only probabilistic approach .
and i think u knows that planets do revolve around the sun constantly , as gravity is the force responsible for that ,
like that same fashion , a electromagnetic force attract the orbiting electrons towards the nucleaus ,
and as electrons are -ve in charge and nucleaus are +ve in charge , so, there is also an electrostatic attraction possible as u knows opp charges attracts each other ,
AND THE FORCE THAT REQUIRES TO SET THE ELECTRON IN MOTION AROUND THE NUCLEAUS IS THE CENTRIPETAL FORCE .
AND IF U CAN REFER TO THE CASE OF YOUR DAY TO DAY LIFE , THEN THINK OF AN ELEVATOR , IT ALSO HAVE SOME LIMIT , IT CANNOT TAKE YOU UNDERGROUND IF IT DOESNOT MADE TO DO SO,
LIKE THAT ONLY , ELECTRONS WILL HAVE TO REVOLVE IN SOME DISTANCE ONLY , AND THAT CANNOT BE MAKE NEARER WHATEVER THE ATTRACTION WILL BE .
HOPE IT CLEARS YOUR DOUBT
ALL THE BEST ..