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Unformatted text preview: The Electronic Structure of Atoms Principles of General Chemistry, 2 nd ed. By M. Silberberg Chemistry, 8th ed. by W. Whitten, R. Davis, R., M. L. Peck, and G. Stanley. Outline 1. The Wave Nature of the Electron 2. The Quantum Mechanical Picture of the Atom 3. Quantum Numbers 4. Atomic Orbitals 5. Electron Configurations 6. Paramagnetism and Diamagnetism 7. The Periodic Table and Electron Configurations Review • The fundamental particles make up atoms: P a rtic le M a s s (a m u ) C h a rg e E le c tro n (e- ) 0 .0 0 0 5 4 8 5 8 -1 P ro to n (p ,p + ) 1 .0 0 7 3 + 1 N e u tro n (n ,n ) 1 .0 0 8 7 0 The Wave Nature of the Electron • according to Louis de Broglie (1925) in his Ph.D. dissertation: – electrons have wave-like properties. – electron wavelengths can be described by the following relationship: particle of velocity v particle of mass m constant s Planck’ h mv h = = = = λ The Quantum Mechanical Picture of an Electron • according to Werner Heisenberg (1927) • it is impossible to determine simultaneously both the position and momentum of an electron (or any other small particle) • also known as Uncertainty Principle – detecting an electron requires the use of electromagnetic radiation which displaces the electron – (today) electron microscopes use this phenomenon The Quantum Mechanical Picture of an Electron • consequently, we must must speak of the electrons’ position about the atom in terms of probability functions • these probability functions are represented as orbitals in quantum mechanics • orbitals- are the volume that the electrons occupy 90-95% of the time (Heisenberg’s Uncertainty principle) Basic Postulates of Quantum Theory 1. Atoms and molecules can exist only in certain energy states. In each energy state, the atom or molecule has a definite energy. When an atom or molecule changes its energy state, it must emit or absorb just enough energy to bring it to the new energy state (the quantum condition). 2. Atoms or molecules emit or absorb radiation (light) as they change their energies. The frequency of the light emitted or absorbed is related to the energy change by a simple equation....
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This note was uploaded on 07/24/2011 for the course CHEM 16 taught by Professor Siao during the Spring '07 term at University of the Philippines Diliman.
- Spring '07