Atomic Theory

Spectra and Bohr's Atom

So let's get back to Bohr, shall we?

Bohr proposed the following atomic model with the detailed consideration of the location of the electron.

1. Each electron in an atom must occupy an energy state with a fixed energy. These energy states are commonly referred to as electron shells.

2. Electrons prefer to be in the lowest energy state possible; in other words, the electrons occupy the lowest energy states first, so the first shell always contains the first electrons. However, as more electrons are added in each successive element on the Periodic Table, the electron shells become full and the electrons are forced to go in the next electron shell.

3. When the atom absorbs energy, the electrons are forced to occupy higher energy states, which are further from the nucleus. The atom is now in the excited state.

4. The electron in the higher energy state (a shell further from the nucleus) immediately returns to a lower energy state (a shell closer to the nucleus). In order for this to occur, the extra energy must be lost.