LECTURE 06 Periodic table

LECTURE 06 Periodic table - Dr P Lucas U of A MSE 110...

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Unformatted text preview: Dr. P. Lucas U of A MSE 110 Electronic structure of atoms SUMMARY FROM LAST CLASS • Bohr’s model provides a rational to the concept of stable orbits however it can not explain all properties of atoms. • The three-dimensional standing waves corresponding to the stable orbits of electrons must be described by three quantum numbers n , m , l . • Each of these orbitals can host two electrons of opposite spin which are described by a fourth quantum number s . • Four quantum numbers are needed to describe each electron in the atom: • n : defines the size of the orbital. n=1, 2, 3, 4… • l : defines the shape of the orbital. l = 0, 1, 2… (n-1) • m : defines the orientation of the orbital. m = -l,…0,…l • s : defines the spin of the electron. s=½, s=-½ Several rules govern the sequence for filling up orbitals: • Aufbau : orbitals of low energy gets filled first. • Pauli : only two electrons of opposite spin in each orbital. • Hund : degenerated orbitals (orbitals of same energy) are filled with unpaired electrons first. Dr. P. Lucas U of A MSE 110 THE PERIODIC TABLE Elements classification: • Each element has a specific number of electrons, the atomic number Z. • As Z increase, the mass and charge of the nucleus increases correspondingly . • These electrons occupy orbitals of increasing energy. • What is a sensible way to organize, classify these elements? Dr. P. Lucas U of A MSE 110 Mendeleev • 1871: While writing a chemistry textbook, Mendeleev realized that many elements had similar chemical and physical properties (colors, melting point, reactivity with oxygen, chlorine, hydrogen) THE PERIODIC TABLE • He also noticed that these properties were repeated periodically with increasing atomic mass. Li 2 O, BeO, B 2 O 3 , CO 2 and Na 2 O, MgO, Al 2 O 3 , SiO 2 Br 2 • Some elements are gaseous at room temperature.Some elements are gaseous at room temperature....
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LECTURE 06 Periodic table - Dr P Lucas U of A MSE 110...

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