1. Another Look at the Atom Objectives: 1. Distinguish between a continuous spectrum and a line spectrum. 2. State the main idea in Bohr's model of the atom. Key Terms: line spectrum, quantum number, ground state, excited state, uncertainty principle

2. Models of the atom 1803 Dalton - tiny indestructible spheres 1897 Thompson - plum pie model 1911 Rutherford - planetary model with electrons in random orbitals 1913 Bohr - orbital model – Niels Bohr, a student of Rutherford, used the information from earlier work to develop his model of the atom.

3. Bohr Model Bohr believed that energy contained in electrons must be quantized to get to different energy orbitals around the atom. He called the energy levels quantums. Each different quantum level is characterized by the letter n (n=1, n=2, n=3,...)

4. Quantized electrons As an electron is quantized it jumps to the next energy level. With sodium above, the outer (valence) electron jumps from n=3 to n=4. When the electron jumps it is considered to be in its exited state. – When in its excited state the electron is farther from the nucleus than is normal. When the excited electron falls back to its normal quantum level a photon is released – The electron is now back at its ground state or resting state

5. Heisenberg's Uncertainty Principle Bohr's planetary model came under some uncertainty and much scrutiny. Heisenberg displayed that is impossible to know where an electron is at any one particular point. You can only be relatively sure where it is not.

6. Quantum Mechanical Model 1926 Erwin Schrodinger - Erwin Schrodinger developed a new model based on the quantum model of Bohr and the observations of Heisenberg. According to his calculations, electrons exist in cloud densities around the nucleus.