Some answers, some more questions
Sujju, I don't exactly know why the electron doesn't collapse into the nucleus, but I'm sure there are mathematical equations that try to answer this question!!!! And something to do with centrifugal force being balanced by the electrostatic attraction explains the elecron's going around the nucleus endlessly and tirelessly.....
1. Why are the sizes of the planets non-uniform (as in not following a particular order, ascending or descending)? Mercury and Venus are small, Earth and intermediate planets are reasonable big and then, Pluto is again small? Why this?