Question

Define energy levels.

Answer 1

From Bohr's model of atom:

1. An atom consists of a small, heavy positively charged nucleus in the center.
2. The negatively charged particles revolve around the nucleus in circular paths called orbits or shells.
3. The orbits are arranged concentrically around the nucleus.
4. These orbits are also known as energy levels or stationary states and have a fixed value of energy.
5. Starting from the nucleus, the different energy levels are numbered as $1,2,3,4,$..… etc. or they are designated as $\mathrm{K},\mathrm{L},\mathrm{M},\mathrm{N},$….. and so on.

Thus,

The circular paths around the nucleus in which electrons revolve are known as energy levels.