Atomic Structure. Based on Inorganic Chemistry, Miessler and Tarr, 4 th edition, 2011, Pearson Prentice Hall

Transcripción

1 Atomic Structure Based on Inorganic Chemistry, Miessler and Tarr, 4 th edition, 2011, Pearson Prentice Hall Images from Miessler and Tarr Inorganic Chemistry 2011 obtained from Pearson Education, Inc.

2 Atomic theory development Democritus ( BCE) atoms (indivisible) Dalton atomic theory (1808), then Avogadro s Law Cannizzaro (1860) everybody should use the same set of atomic weights!!! Mendeleev and Meyer (1869) periodic table

3 Cuándo los elementos fueron descubiertos? 8.1

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5 Propiedad a describir Predicción de eka-silicio hecha en el 1871 Propiedades del Germanio descubierto en 1886 Peso atómico Densidad (g/cm 3 ) Calor específico (J/g-K) Punto de fusión ( o C) Alto 947 Color Gris oscuro Blanco grisáceo Fórmula del óxido XO 2 GeO 2 Densidad del óxido (g/cm 3 ) Fórmula del cloruro XCl 4 GeCl 4 Punto de ebullición del cloruro poco menor de Cómo te quedó el ojo?

6 Other important discoveries

7 Bohr Atom Balmer (1885) showed that energies of visible light emitted by H atom were given by the ecuation Then, it was replaced by Given that n l < n h

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9 Dual nature of electron de Broglie Heisenberg s uncertainty principle

10 Schrödinger Equation ĤΨ = EΨ Propiedades de Ψ Ψ tiene que ser single-valued Ψ Ψ y su primera derivada tienen que ser contínuas Ψ tiene que aproximarse a 0 mientras r se acerca a La probabilidad de un electrón estar en algún punto del espacio tiene que ser igual a 1 Todos los orbitales en un átomo tienen que ser ortogonales unos con los otros. En algunos casos, esto significa que sus ejes tienen que ser perpendiculares.

11 La partícula en la caja!!! La energía potencial entre x=0 y x=a es definida como cero Fuera de la caja, V(x) es infinita No hay fuerzas actuando en la partícula dentro de la caja

12 Wave functions for particle in a box Cuadrado de la función de onda densidad de probabilidad

13 Particle in a box (n=1)

14 Particle in a box (n=2)

15 Particle in a box (n=3)

16 Atoms are tridimensional n, l and m l m s is a result of a relativistic correction accounting for the magnetic moment of the electron

17 Función radial vs angular La función angular determina cómo la probabilidad cambia en una distancia fija desde el centro La función de probabilidad radial (4πr 2 R 2 ) describe la probabilidad de encontrar al electrón en un punto desde el centro (sumados todos los ángulos) Una superficie nodal es en la cual la probabilidad es cero Un nodo angular es plano o cónico Un nodo radial (también llamado esférico) es esférico. Su cantidad está dada por n l 1

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24 Aufbau principle Building of electrons in atoms results from continually increasing the quantum numbers This results in the electronic configuration Example: Selenium (Z=34) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 4 *Lowest total energy for the atom *Pauli exclusion principle applies

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26 Hund s rule of maximum multiplicity Electrons will be placed in orbitales so as to give the maximum total spin possible (or the maximum number of parallel spins) Two electrons in the same orbital have a higher energy than two electrons in separate orbitals, caused by electrostatic repulsion This results in a Coulombic energy of repulsion (Π c ) which is positive The multiplicity will be the number of unpaired electrons plus 1 (n + 1) This is the number of possible energy levels that depend on the orientation of the net magnetic moment in a magnetic field.

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28 Exchange energy (Π e ) How many possible exchanges between two electrons with the same energy and the same spin? Exchange energy (negative) = number of times x Π e

29 Shielding Any electron between the nucleus and another electron shields the nuclear charge Imagine being at the theather Z* = Z S

30 Shielding n is the most important in determining energy l becomes important in polyelectronic atoms ( e- > 1) The net result is the electronic configuration we learn at general chemistry courses 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, etc.

31 Slater s rules for determining S for a specific electron Write the electronic configuration in the regular order Rearrange the configuration as: (1s) (2s, 2p) (3s, 3p) (3d) (4s, 4p) (4d) (4f) (5s, 5p) (5d) (5f) etc Electrons in groups to the right of your electron of choice does not contribute to S If your electron of choice is located in ns or np Each electron in the same group contributes 0.35 to S (exception is 1s electrons which contribute 0.30) Each electron in n-1 groups contribute 0.85 to S Each electron in n-2 groups contribute 1 to S

32 Slater s rules for determining S for a specific electron If your electron of choice is located in nd or nf Each electron in the same group contributes 0.35 to S Each electron to the left 1 to S Practice Calculate S and Z* for a 3p electron in sulfur (S) Calculate S and Z* for a 3d and a 4s electron in nickel (Ni)

33 Justification of Slater s rules 1. They work!!! 2. Electron probability curves for s and p orbitals higher probability near the nucleus than d and f orbitals If you were to compare (2s, 2p) (3s, 3p) (3d) calculated as 100% effective (2s, 2p) (3s, 3p) (3d) - calculated as 85% effective Bold electrons are the electron of choice Underline electrons are the shields Why??? 3s and 3p electrons have a significant probability near the nucleus

34 Periodic properties of atoms Ionization energy (energy required to remove an electron from a gaseous atom or ion)

35 Electron affinity (energy required to remove an electron) Table obtained from Chemistry Chang 10 th ed 2010

36 Atomic radii Covalent radii (ideal nonpolar molecules)

37 Ionic radii depends on coordination number covalent character of the bonding distortions of regular crystal geometries delocalization of electrons Anion size is also influenced by cation s size and charge

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