ATOMIC SPECTRA
The Bohr model was based on a simple postulate. Bohr applied to the hydrogen
atom the concept that the electron can exist only in certain energy levels without
an energy change but that, when the electron changes its state, it must absorb or
emit the exact amount of energy that will bring it from the initial state to the final
state. The ground state is the lowest energy state available to the electron. The
excited state is any level higher than the ground state. The formula for a change
in energy (ΔE) is:
When an electron moves from the ground state to an excited state, it must
absorb energy. When it moves from an excited state to the ground state, it emits
energy. This release of energy is the basis for atomic spectra. (See Figure 6.)
The energy values shown were calculated from Bohr’s equation.
TIP
When electrons drop to the lowest available energy level, they release energy.