Bohr’s Model Why don’t the electrons fall into the nucleus? Move like planets around the sun. In circular orbits at different levels. Amounts of energy separate one level from another.

Bohr’s Model Electrons can have only certain orbits corresponding to different amounts of energy called quantum (“quanta” is plural). Bohr used a simple model for hydrogen  He labeled each energy level using a quantum number, n The ground state, closest to the nucleus, has n=1 

Bohr’s Model When an electron absorbs radiation (the appropriate amount of energy), it jumps to a higher energy level called excited state, n=2, n=3, and so on. When the electron jumps down to the n=1 level from an excited state, there is an emission of radiation.

} Bohr’s Model Further away from the nucleus means more energy. Fifth There is no “in between” energy Energy Levels Fifth Fourth Third Increasing energy Second First Nucleus

The Quantum Mechanical Model Energy is quantized. It comes in chunks. A quanta is the amount of energy needed to move from one energy level to another. Since the energy of an atom is never “in between” there must be a quantum leap in energy.