Q1.
You may be wondering, how does Bohr’s model explain stability?
Answer
By a postulate: the allowed circular paths are stationary states, and in a stationary state an electron's energy stays constant even though it is moving.
Set the two models side by side.
| Rutherford | Bohr | |
|---|---|---|
| Electron path | any circular orbit | only certain fixed shells K, L, M, N (n = 1, 2, 3, 4) |
| Energy while orbiting | continuously radiated away | constant — no loss |
| Predicted fate | spirals into the nucleus; atom collapses | stays in its shell; atom is stable |
| Energy change | continuous | only in jumps, equal to the gap between two levels |
The energy of the levels rises as you go outward: K (n = 1) is closest to the nucleus and lowest in energy; an electron in L (n = 2) has more energy than one in K. An electron changes shell only by absorbing or releasing exactly the energy difference between the two levels — nothing in between is allowed, so there is no smooth spiral inward.
Why it happens: Bohr did not derive stationary states; he assumed them because they made the model match experiment, especially the sharp lines seen in atomic spectra. That is what a postulate is — an assumption judged by the results it produces. Quantum mechanics later explained why only certain energies are allowed.