Chapter 8 -lecture 1

Chapter 8 -lecture 1 - General Chemistry I Fall 2007 Joann...

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Unformatted text preview: General Chemistry I Fall 2007 Joann S. Monko Chemistry 9th ed. Raymond Chang spdf notation Write the ground-state electron configurations for the following: Mg P Cu Mg+2 P-3 (long version and Noble gas config.) 3 Clicker Question This the ground state configuration for what element? 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 a. Tc b. Br c. Cl d. Zn e. Ca Electron Spin Quantum Number Diamagnetic - NOT attracted to a magnetic field Paramagnetic - attracted to a magnetic field Substance has unpaired e-'s Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. General Periodic Trends Atomic and ionic size Ionization energy Electron affinity 5 Higher effective nuclear charge Electrons held more tightly Larger orbitals. Electrons held less tightly. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. 6 Atomic Size Size goes UP - going down a group -e-'s further away from nucleus -less attraction Size goes DOWN - going across a period -e-'s pulled closer, held tighter Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Atomic Radii 7 Size decreases across a period due to increased Z*. Each added electron feels a greater and greater + charge. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Trends in Atomic Size Radius (pm) 250 8 K 3rd period 2nd period Na Li 1st transition series 200 150 100 Kr Ne Ar 50 He 0 0 5 10 15 20 25 30 35 40 Atomic Number Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Sizes of Transition Elements 9 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Sizes stay about the same. Chemistries are similar! Ion Sizes + Li, 152 pm 3e and 3p Li + , 78 pm 2e and 3 p 10 Forming a Cation e- / p+ attraction has gone UP size DECREASES F, 71 pm 9e and 9p F , 133 pm 10 e and 9 p Forming an Anion e- / p+ attraction has gone DOWN size INCREASES Trends in ion sizes are the same as atom sizes. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. 11 Chang Chemistry, 8th ed. 12 Clicker Question Arrange the following isoelectronic species in order of increasing ionic radius: O F Na Mg -2 -1 +1 +2 1. O-2 < F-1 < Na+1 < Mg+2 2. F-1 < O-2 < Mg+2 < Na+1 1. Mg+2 < Na+1 < F-1 < O-2 Ionization Energy Energy required to remove an e- from an atom in the gas phase. 13 Mg (g) + 738 kJ Mg+ (g) + eMg+ (g) + 1451 kJ Mg2+ (g) + eMg has 12 p+ & only 11 e-'s. + IE + 7733 Mg. Mg (g) for Mg > kJ Mg (g) + eKotz &Treichel Chemistry & Chemical Reactivity 5th ed. Energy cost + too high NO Mg 1st Ionization energy (kJ/mol) 2500 He 14 Ne Trends in Ionization Energy Ar Kr 2000 1500 1000 500 0 H 1 Li 3 5 7 9 Na 11 13 15 17 19 K 21 23 25 27 29 31 33 35 Atomic Number IE increases across a period cuz' Z* increases. IE decreases down a group cuz' size increases. Metals lose electrons more easily than nonmetals. Nonmetals lose electrons with difficulty. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. 15 Lithium Sodium Periodic Trends Reactivity of Alkali Metals with Water reactivity - a group Potassium Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Electron Affinity 16 the energy involved when an atom gains an eto form an anion. X (g) + e- ---> X (g) E.A. = - E O atom [He] - + electron O - ion [He] E is EXOthermic cuz O has an affinity for an e-. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. EA = + 141 kJ Electron Affinity of Nitrogen N atom [He] 17 E is zero for N due + electron N- ion [He] EA = 0 kJ Atom EA F +328 kJ to electron-electron Cl +349 kJ repulsions. Br +325 kJ I +295 kJ Trends: EA increases across a period ( - becomes more positive). EA decreases down a group ( - becomes less positive). Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. 18 Kotz &Treichel Chemistry & Chemical Reactivity Chang 5th ed. Chemistry, 8th ed. 19 Clicker Question Arrange the following in order of increasing first ionization energy Na, Cl, Al, S, Cs 1. Cs < Cl < Al < S < Na 2. Cs < Na < Al < S < Cl 3. Al < Na < Cs < S < Cl 4. Na < Cs < Al < Cl < S 20 2 Forms of Chemical Bonds Ionic -- complete transfer of 1 or more e-'s from one atom to another Covalent -- some valence e-'s shared between atoms Most bonds are somewhere in between. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Forms of Chemical Bonds Ionic Bonding: complete e- transfer from an element of low IE (metal) to an element of high affinity for e-'s (nonmetal) 2 Na (s) + Cl2 (g) 2 Na+ + 2 Cl metals (Grps 1A & 2A & transition metals) + nonmetals (O & halogens) = ionic bonds 21 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Covalent Bonding 2 nuclei are attracted to the same e-'s -a bond forms from Electron sharing 22 HA + HB HA HB Bond is a balance of attractive and repulsive forces. Chemical Bonding Objectives are to understand: 1. valence e- distribution in molecules and ions. 2. molecular structures 3. bond properties & effect on molecular properties. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Valence Electrons Outer shell e-'s - used in bonding. Group 1 2 3 4 5 6 7 e- Configuration ns1 ns2 ns2np1 ns2np2 ns2np3 ns2np4 ns2np5 Valence e1 2 3 4 5 6 7 23 e- Distribution in Molecules 24 Valence electrons are distributed as shared or BOND PAIRS and unshared or LONE PAIRS. G. N. Lewis 1875-1946 H Cl shared or bond pair lone pair (LP) LEWIS ELECTRON DOT structure Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. 25 Chang Chemistry, 8th ed. ...
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This note was uploaded on 04/08/2008 for the course CHEM 100 taught by Professor Monko during the Winter '08 term at Kutztown.

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