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Quantum Theory and Electron Configurations. Quantum Theory. In 1926, Austrian physicist Erwin Schrodinger used the idea that electrons have a dual wave/particle nature and created an equation using electrons as waves … with Heisenberg…
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Quantum Theory • In 1926, Austrian physicist Erwin Schrodinger used the idea that electrons have a dual wave/particle nature and created an equation using electrons as waves… with Heisenberg… • and developed the foundation for the modern quantum theory: • We can only know the probability of finding an electron, not it’s exact location.
The Quantum Model of the Atom • There are four quantum numbers that describe the posititon of an electron in an atom.
Quantum Numbers • Each electron in an atom has a set of four unique quantum numbers. • Principal Quantum Number (n) • Angular Momentum Quantum Number (sublevel) (l) • Magnetic Quantum Number (orbital) (m) • Spin Quantum Number (s)
Principal Quantum Number • Indicates the main energy levels occupied by the electron. The number of electrons that can fit in a shell is: 2n2
Angular Momentum Quantum Number • The angular momentum quantum number indicates the shape of the orbital.
Magnetic Quantum Number • Magnetic Quantum number indicates the orientation of the orbital around the nucleus. s-orbital
Spin Quantum Number • Spin Quantum Number indicates the direction of spin.
Electron Configurations There are three rules explaining how electrons are arranged outside of the nucleus: • Aufbau Principle • Pauli Exclusion Principle • Hund’s Rule
Aufbau Principle • Electrons occupy the lowest energy orbital that can receive it.
Wolfgang Pauli • Pauli Exclusion Principal – no two electrons can have the same four quantum numbers.
Hund’s Rule • All orbitals of equal energy are occupied by one electron before any electrons can pair up…
Valence Electrons • Valence electrons are the electrons in the highest occupied energy level…. • Example: Lithium: 1s22s1 Level two is the highest occupied energy level… there is one valence electron • Example: Chlorine: 1s22s22p63s23p5 Level three is the highest occupied energy level. Chlorine has 7 valence electrons • Example: Selenium: 1s22s22p63s23p64s23d104p4 Level four is the highest level. Selenium has 6 valence electrons.
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