Week of Notes 9/26-10/2
Week of Notes 9/26-10/2 CH 101
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This 6 page Class Notes was uploaded by Rani Vance on Sunday October 4, 2015. The Class Notes belongs to CH 101 at University of Alabama - Tuscaloosa taught by a professor in Fall 2015. Since its upload, it has received 27 views. For similar materials see General Chemistry in Chemistry at University of Alabama - Tuscaloosa.
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Date Created: 10/04/15
Chemistry 101 Week of Notes 928102 Chapter 4 continued Periodic Trends Clicker Question Calculate the effective nuclear charge for valence electrons for carbon and uorine What are the consequences Answer F valence electrons will be held closer to the nucleus even though there are more of them Clicker Question Choose the larger atom Answer N is larger and F Ge is larger than C calculate the effective nuclear charge to figure out this problem Shielding in a multielectron system electrons are simultantelously attracted to the nucleus and repelled by each other outer electrons are shielded from the nucleus outer electrons do not experience the full strength of the nucleus Effective Nuclear Charge effective nuclear character is the net positive charge that is attracting a particular electron Zeffective Z39S Z atomic nuclear charge S of electrons in lower energy levels electron in the same energy level provide little to no shielding e9 valence 2s1 electron Affective 28 9 core electron 1s2 09 nucleus 3 321 Calculate the Effective Nuclear Charge 1 B91s22s22p1 Valence 2s2 2p1 Affective 289 5valence 2core 3 2 C9 1s2 2s2 2p2 Valence 2s2 2p2 Zeffective ZS9 6valence 2core 4 3 N91s22s2 2p3 Valence 2s2 2p3 Affective ZS9 7valence 2core 5 even in an element has a large number of valence electrons they are held more closely to the nucleus than an element With a smaller number of valence electrons Explanation for the Group Trend in Atomic Radius the larger the orbital the farther the electron Will be from the nucleus traversing down a group column adds a principle quantum number bigger n bigger orbital bigger atom as you move from the top of the column to the bottom of the column the size of the atoms increase Trends in Ionic Radius ions that form from the same elements of the group column have the same charge ion size increases down the column smalllarge H Li Na K Rb Cs Li and Be2 9 the larger positive charge smaller cation 0239 and F39 9 larger negative charge larger anion Quantum Mechanical Explanation for Trends in Cation Radius atoms form cations increased energies are removed always removed valence electrons ie Na 9 1s2 2s2 2p6 3s1 remove the valence electron 9 Na 1s2 2s2 2p6 930 lltey concept if there is a larger the amount of protons then the electrons are pulled in tighter Electron Configurations of main group anions in the ground state anions form When the atom gains electrons in the valence shell Ex K 1s2 2s2 2p6 3s2 3p6 4s1 K 1s2 2s2 2p6 3s2 3p6 4s0 Ionization Energy energy needed to remove an electron from an atom M9 M e39 valence electrons are easiest to remove the larger the Zeff the harder electrons are to remove ionization energy increases moving right to left ionization increases moving up columns Clicllter question Which Will have the smallest ionization energy B Be Mg Ca Answer Ca Exceptions to the trends in 1st IE ionization energy trends Be high B low ls2 2s2 ls2 2s2 2p1 N high 0 low ls2 2s2 2p3 ls2 2s2 2p4 It is easier to remove paired electrons than unpaired electrons Trends in successive ionizing energies each successive electron requires more energy to remove core electrons are very hard to remove metals want to lose electrons nonmetals want to gain electrons Recitation Electron Affinity M e39 9 M Metallic Character is how closely an element s properties match an ideal metal metallic character decreases from left to right on the periodic table metallic character increases when moving down the columns of the periodic table Lewis Structure compounds can be molecular or ionic molecular compounds composed of two or more covalently bonded nonmetals discrete entities ionic compounds composed of metal cations and non anions held together by ionic bonds usually form extended 30 lattice formula with NaCl Types ionic NaCl covalent ice water metallic selenium interact but remain separate Bonding Theories chemists have developed how and why atoms attach together to form molecules Some can be stable and others not can be used to predict shapes as well as chemical properties Why do atoms bond chemical bonds lower the potential energy between charged particles that compose the atom Forces that in uence bonding nucleus to nucleus repulsion electron to electron repulsion nucleus to electron attraction Lewis Bonding Theory emphasizes valence electron to explain bonding we draw lewis structures allow us to predict molecular stability shape size and polarity Determining the number of valence electrons in an atom column number on periodic table will tell you how many valence electrons a main group has in a lewis structure represent valence electons of main group elements as dots surrounding symbol Dots valence Symbol nucleus an inner electrons