handout_L16_Polyatomic_Peroidic Trend

Handout_L16_Polyatom - Lecture 16A Polyelectronic Atoms Reading Zumdahl 12.10-12.13 Outline Spin The Aufbau Principle Filling up orbitals and the

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Lecture 16A: Polyelectronic Atoms • Reading: Zumdahl 12.10-12.13 • Outline: – Spin – The Aufbau Principle – Filling up orbitals and the Periodic Table Spin • Further experiments demonstrated the need for one more quantum number. • Specifically, some particles (electrons in particular) demonstrated inherent angular momentum. Spin (cont.) • The new quantum number is m s (analagous to m l ). • For the electron, m s has two values: +1/2 and -1/2 m s = 1/2 m s = -1/2 The Aufbau Principal • For polyelectronic atoms, a direct solution of the Schrodinger Eq. is not possible. • When we construct polyelectronic atoms, we use the hydrogen-atom orbital nomenclature to discuss in which orbitals the electrons reside. • This is an approximation (and it is surprising how well it actually works). The Aufbau Principal (cont.) • When placing electrons into orbitals in the construction of polyelectronic atoms, we use the Aufbau Principle. • This principle states that in addition to adding protons and neutrons to the nucleus, one simply adds electrons to the hydrogen-like atomic orbitals • Pauli exclusion principle: No two electrons may have the same quantum numbers. Therefore, only two electrons can reside in an orbital (differentiated by m s ). The Aufbau Principal (cont.) • Finally, orbitals are filled starting from the lowest energy. • Example: Hydrogen 1s 2s 2p • Example: Helium (Z = 2) 1s 2s 2p 1s 1 1s 2
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The Aufbau Principal (cont.) • Lithium (Z = 3) 1s 2s 2p 1s 2s 2p • Berillium (Z = 4) • Boron (Z = 5) 1s 2s 2p 1s 2 2s 1 1s 2 2s 2 1s 2 2s 2 2p 1 The Aufbau Principal (cont.) • Carbon (Z = 6) 1s 2s 2p 1s 2s 2p • Nitrogen (Z = 7) Hund’s Rule : Lowest energy configuration is
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This note was uploaded on 01/18/2012 for the course CHEM 152A taught by Professor Chiu during the Winter '12 term at University of Washington.

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Handout_L16_Polyatom - Lecture 16A Polyelectronic Atoms Reading Zumdahl 12.10-12.13 Outline Spin The Aufbau Principle Filling up orbitals and the

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