Chapter 7 - Chapter 8

Chapter 7 - Chapter 8 - 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 Arrangement of Electrons in Atoms e-'s are arranged as Each orbital can contain no more than 2 e-'s! SHELLS (n) SUBSHELLS (l) The 4th quantum number: Electron Spin, ms Experimental proof: an electron has a spin. Two spin directions are given by ms where ms = +1/2 and 1/2. ORBITALS (ml) Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Electron Spin Quantum Number Diamagnetic: NOT attracted to a magnetic field Paramagnetic: substance is attracted to a magnetic field. Substance has unpaired e-'s. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Quantum Numbers n ---> shell l ---> subshell ml ---> orbital 1, 2, 3, 4, ... 0, 1, 2, ... n - 1 -l ... 0 ... +l ms ---> electron spin +1/2 and -1/2 Pauli Exclusion Principle No two electrons in the same atom can have the same set of 4 quantum numbers. Each electron has a unique address. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Clicker Question What are the Quantum Numbers for the 5th electron of boron? A. n = 1, l = 1, ml = -1, ms = +1/2 B. n = 2, l = 1, ml = 0, ms = +1/2 C. n = 2, l = 1, ml = -1, ms = +1/2 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Assigning Electrons to Subshells H atom: all subshells of same n have same energy. In many-electron atom: a) subshells increase in energy as value of n + l increases. b) for subshells of same n + l, subshell with lower n is lower in energy. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Electron Filling Order Writing Atomic Electron Configurations Two ways of writing configs. first: spdf notation for H, atomic number = 1 spdf notation 1s value of n 1 no. of electrons value of l Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Writing Atomic Electron Configurations Two ways of writing configs: Other is called the orbital box notation. ORBITAL BOX NOTATION for He, atomic number = 2 Arrows 2 depict electron spin 1s 1s One electron has n = 1, l = 0, ml = 0, ms = + 1/2 Other electron has n = 1, l = 0, ml = 0, ms = - 1/2 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Electron Configurations and the Periodic Table Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Lithium Group 1A Atomic # = 3 1s22s1 3 total e-'s 3p 3s 2p 2s 1s Beryllium Group 2A Atomic # = 4 1s22s2 4 total e-'s 3p 3s 2p 2s 1s Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Boron Group 3A Atomic # = 5 1s2 2s2 2p1 5 total e-'s 3p 3s 2p 2s 1s Carbon Group 4A Atomic # = 6 1s2 2s2 2p2 6 total e-'s 3p HUND'S RULE: most stable arrangement max. # of unpaired e-'s with same spin. 3s 2p 2s 1s Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Nitrogen Group 5A Atomic # = 7 1s2 2s2 2p3 7 total e-'s 3p 3s 2p 2s 1s Oxygen Group 6A Atomic # = 8 1s2 2s2 2p4 8 total e-'s 3p 3s 2p 2s Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. 1s Fluorine Group 7A Atomic # = 9 1s2 2s2 2p5 9 total e-'s 3p 3s 2p 2s 1s Neon Group 8A Atomic # = 10 1s2 2s2 2p6 10 total e-'s 3p 3s *End of the 2nd period 2p 2s 1s *The 2nd shell is full! Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Sodium Group 1A Atomic # = 11 1s2 2s2 2p6 3s1 or "neon core" + 3s1 [Ne] 3s1 Rare Gas Notation All Group 1A elements have [core]ns1 configurations. Aluminum Group 3A Atomic # = 13 1s2 2s2 2p6 3s2 3p1 [Ne] 3s2 3p1 3p 3s 2p 2s 1s Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. All Group 3A elements have [core ] ns2 np1 configurations where n is the period number. Transition Element Configurations 3d orbitals used for Sc-Zn Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. 4f orbitals used for Ce - Lu 5f for Th - Lr Ce [Xe] 6s2 5d1 4f1 Uranium [Rn] 7s2 6d1 5f3 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Chapter 8 PERIODIC TRENDS Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. General Periodic Trends Atomic and ionic size Ionization energy Electron affinity Higher effective nuclear charge Electrons held more tightly Larger orbitals. Electrons held less tightly. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Atomic Size Size goes UP on going down a group. Because e-'s are added further from the nucleus, there is less attraction. Size goes DOWN on going across a period. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Atomic Radii 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 K 200 3rd period 2nd period Li Na 1st transition series 150 Kr 100 Ar Ne 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 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. 3d subshell is inside the 4s subshell. 4s electrons feel a more or less constant Z*. Ion Sizes + Li, 152 pm 3e and 3p Li + , 78 pm 2e and 3 p Forming a cation. *CATIONS are SMALLER than the atoms from which they come. *The e- / p+ attraction has gone UP size Forming an DECREASES. F, 71 pm F - , 133 pm anion. 9e and 9p 10 e and 9 p *ANIONS are LARGER than the atoms from which they come. *The 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. Chang Chemistry, 8th ed. ...
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