DESCRIP INORGANIC CHEM
DESCRIP INORGANIC CHEM CHEM 362
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This 22 page Class Notes was uploaded by Bret Mills on Wednesday October 21, 2015. The Class Notes belongs to CHEM 362 at Texas A&M University taught by Kim Dunbar in Fall. Since its upload, it has received 34 views. For similar materials see /class/226236/chem-362-texas-a-m-university in Chemistry at Texas A&M University.
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Date Created: 10/21/15
LECTURE 3 Q Reaction Pro le What is it A It is a graph of free energy G versus the pathway of the reaction The pathway is the change in bond distances during the conversion from reactants to products eX Decomposition of formic acid o Iquot J 5 54th rcuh39onka coral ina Q Based on the reaction pro le how can one increase the rate of a reaction A For one thing we cannot change the value of the Equilibrium constant K unless we change the reaction conditions ternp pressure solvent etc but we can alter the rate without changing the reaction conditions by adding a catalyst A Catalyst lowers the AG 75 Activation Energy Two Ways 1catalysts can assist in forming the activated cornpleX 2catalysts can provide an entirely different pathway by temporarily binding to the reactants Continuing with the review Electronic Structure Chapter 2 Atomic Electronic Structure The a number and b distribution of electrons around an atom These two features essentially dictate the properties of the atom First hints about the electronic structure of atoms came from eXperimental work carried out in late 1800 s amp early 1900 s Absorption and Emission of radiation from atoms was welldocumented but not at all understood 0 Not until 1913 were any theories advanced that could even eXplain the emission spectrum of Hydrogen This was when Rydberg realized that the emission lines had speci c wave numbers but he could not reconcile this relationship with classical physics which said the e39 would spiral into the nucleus and emit a continuum of energies o In 1913 Bohr broke from classical physics and said there are Discrete Quantized Levels where an electron can reside in an atom He related the angular momentum mvr to an integer value Quantized Value mvr 271 m is the mass v is velocity r is radius h is Planck s const n is an integer value Emission Spectrum of Hydrogen um rrglun Inn mm m um Ibmm Iwr39r mum 1 x In wm mm InHHu wmm uyu m 1 r Wu mm m I m Bohr orbits and the transitions associated with emissions from higher orbits to orbits n 1 n 2 n 3 Q Is the Bohr atom model capable of being extended to other atoms besides H AND Q Why A Electrons are not discrete particles with precisely de ned positions and velocities Bohr himself used the idea put forth by Max Planck that electromagnetic energy photons or any wave is quantized E W Planck s constant gt Electrons have the same wavelike properties that photons have Dawn of Dual ParticleWave Theories Igt Wave Mechanics Two important players W All particles with velocities v and A hmv mass m can be described by a Ezrgglghwaw wavelength Proposed a W general HLP ELF mathematical expression for Wave equation an electron The Theory of Wave Mechanics is the method of operator algebra H Hamiltonian operator de nes a series of operations to perform LP Wave function describes the e39 in terms of its wave properties PRI 9 9 CD P w w Radial angular Wave functions have two components The physical manifestation of 1 is what we call an orbital Orbitals have 1 shape determined by angular part 2 extension determined by radial part or size The most simplistic way that these two are depicted is in the form of boundary surface diagrams our usual meaning of an orbital 351 31 axis 345 3355 ng rd w 3m km aim mum I N N Eggs EmmaMa Digngwu Zx v ak y y x A Y 3deJI 342 aw Felecia W Nudist whim is 1W modl W The square of 1 1 2 gives a measure of the e39 density in various regions Q How does the Bohr model compare to the wave function model A The precise orbit of an e39 in a Bohr orbit is the place where the e39 density probability is the highest Bohr model dot density e39 density diagram probability function Another way to show how the e39 density or probability for nding the e39 varies in an orbital is a contour map 2p 3p mm W m m 0th gt4 1 nzo nnnm i There are major differences that arise because of the function 41tr2Rr2 which is the e39 density probability function L l e density probability functions 47ch Rr2 1s 1 III T E A or 1 L l I r a quotquot5 no probability of the e39 at the nucleus I t I39 E 31 r1gtr aquot IF39rHW r2Rr2 for short 2s 1 393 17 quotquot39I 2 l r 7 E l j l IF quot l f 393 E j I quot WI for a 2p orbital the e39 density increases to a maximum then drops off 3p is different Summary of Quantum numbers for an electron n principal QN n can be 0 gt 00 11 determines the size of the orbitals i orbital Q N i O12n1 determines the shape of orbitals mg o 1 mgi10etc ms i 12 for each election Four QN s in all n 1 shell EO 1s 11 2 shell EO 2s E1 2p n 3 shell O 3s El 3p 32 3d eta Electronic Configuration The term used to describe the manner in which electrons are arranged in an atom l Aufbau Principle Add electrons from the lowest to the highest levels 2 Hund s Rule of maximum multiplicity Add electrons in orbitals of the same energy degenerate set with same spin before pairing spins eg ls2s22p63s23p64s23d4 is l ll ll ll l l l l 4s 3d 45 3d X I Pauli Exclusion Principle No two electrons can have the same 4 Quantum numbers in other words if two electrons are in the same shell 11 same set of orbitals E and same exact orbital mg then they would have different values of n1S spins 12 for one and 12 for the other Both electrons mg 1 n2 2p 1 111321 but ms 12 for one and niS 12 for other Fiwe 727 Exsug Copyug Figag e 72a A xeua brawn Whack in a w MW 15 M W equot A Q w SW W 0 Mai114 Knowledge of Atomic Structure is so important because it allows us to understand the periodic relationships among elements Concepts that follow from Electronic Structure 1 The interpenetrations of atomic orbitals which depends on size amp shape in other words how they fit together 2 Because of their interpenetration we order the orbitals in the Aufbau way Is 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 3 Because of the different interpenetrations and orientations of the orbitals the electrons eXperience different nuclear charges and finally MAIN POINT 4 Properties Such as o Ionization Energies 0 Atomic amp Ionic Sizes 0 Electron Af nities o ElectronegatiVities Re ect on the Electronic Con guration of a group column and a period row Ionization Energy or EnthalpV AHion in kJmol First Ionization Energy Three trends are noticeable 1 Maximum at Noble Gases 2 Minimum at alkali metals closedshell is favored 3 The increase in going from alkali metal to noble gas eg Na to Ar for example is not regular gt there are two dips Q Why A Because of differences in shielding of s amp p orbitals Shielding When you put electrons in orbitals with the same Quantum number 11 same shell as you keep adding more they are less shielded from the positive charge of the nucleus The leads to it being more difficult to remove electrons higher LE in other words The Effective Nuclear Charge increases as you go across a row Squot 39 3 Y 7 Y M Wankel No A rats p clcdwn U beln eclch ch shielded Q Why do the changes at Al and S happen A Because Na is 2s1 Mg is 2s2 Al is 2s22p1 it is favored to lose the one p electron to go back to a filled subshell S is 2s22p4 it is easier to lose an electron to get it back to the stable halffilled subshell 2s 2p