Transcript Another Look at the Atom

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
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.
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, ...)
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
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.
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.