ElectronConfigs - ATOMIC ELECTRON CONFIGURATIONS AND...

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Unformatted text preview: ATOMIC ELECTRON CONFIGURATIONS AND PERIODICITY 1 2 3 Arrangement of Electrons in Atoms Arrangement of Electrons in Atoms Electrons in atoms are arranged as Each orbital can be assigned no more than 2 electrons! SHELLS (n) This is tied to the existence of a 4th electron electron spin quantum number, ms. SUBSHELLS (l) quantum number, the quantum ORBITALS (ml) 4 Electron Spin Quantum Number, ms Can be proved experimentally that electron Can be proved experimentally that electron has a spin. Two spin directions are given by has a spin. Two spin directions are given by mss where mss = +1/2 and -1/2. m where m = +1/2 and -1/2. Electron Spin Quantum Number 5 6 QUANTUM QUANTUM NUMBERS NUMBERS n ---> shell n ---> shell Diamagnetic :: NOT attracted to a magnetic Diamagnetic NOT attracted to a magnetic field field Paramagnetic :: substance is attracted to a Paramagnetic substance is attracted to a magnetic field. Substance has unpaired magnetic field. Substance has unpaired magnetic unpaired electrons . electrons. Page 1 1, 2, 3, 4, ... 1, 2, 3, 4, ... ll ---> subshell ---> subshell 0, 1, 2, ... n -- 1 0, 1, 2, ... n 1 mll ----> orbital m --> orbital -ll ... 0 ... +l --l ... 0 ... +l mss ----> electron spin m --> electron spin +1/2 and -1/2 +1/2 and -1/2 7 Pauli Exclusion Principle When n = 2, then l = 0, 1 2s orbital And many more! And many more! 6e- TOTAL = 9 2e2e- three 2p orbitals three Electrons in Atoms Electrons in Atoms When n = 3, then ll = 0, 1, 2 When n = 3, then = 0, 1, 2 3s orbital 2e2e3s orbital 2ethree 3p orbitals 6etthree 3p orbitals hree 6efive 3d orbitals 10effive 3d orbitals ive 10eTOTAL = 18e18eTOTAL = 18e- this shell has a single orbital (1s) to this which 2e- can be assigned. That is, each electron has a unique address. When n = 4, then l = 0, 1, 2, 3 4s orbital 2e2ethree 4p orbitals 6ethree five 4d orbitals 10efive seven 4f orbitals 14eseven TOTAL = 32e32e- 8 When n = 1, then l = 0 No two electrons in the same atom can have the same set of 4 quantum numbers. Electrons in Atoms Electrons in Atoms Electrons in Atoms Electrons in Atoms 8e8e- 10 11 Assigning Electrons to Atoms Assigning Electrons to Atoms •• Electrons generally assigned to orbitals of Electrons generally assigned to orbitals of successively higher energy. successively higher energy. •• For H atoms, E = -- C(1/n 22). E depends only For H atoms, E = C(1/n ). E depends only on n. on n. •• For many-electron atoms, energy depends For many-electron atoms, energy depends on both n and l. on both n and l. •• See Figure 8.6, page 342 and Screen 8. 5. See Figure 8.6, page 342 and Screen 8. 5. Page 2 12 Assigning Electrons to Subshells • In 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. 13 14 Effective Nuclear Charge Electron Filling Order • Z* is the nuclear charge experienced by the outermost electrons. See p. 344 and The reason for difference in energy for 2s and 2p subshells, for example, is effective nuclear charge, Z*. Screen 8.6. • Explains why E(2s) < E(2p) • Z* increases across a period owing to incomplete shielding by inner electrons. • Estimate Z* by --> [ Z - (no. inner electrons) ] Estimate • Charge felt by 2s e- in Li Z* = 3 - 2 = 1 • Be Z* = 4 - 2 = 2 Be Z* •B Z* = 5 - 2 = 3 and so on! Z* Figure 8.7 16 Writing Atomic Electron Writing Atomic Electron Configurations Configurations Two ways of Two ways of writing configs. writing configs. One is called One is called the the spectroscopic spectroscopic notation. notation. SPECTROSCOPIC NOTATION for H, atomic number = 1 1 1s value of n no. of electrons value of l Writing Atomic Electron Writing Atomic Electron Configurations Configurations Two ways of Two ways of writing writing configs . Other configs. Other is called the is called the orbital box orbital box notation. notation. 15 Effective Nuclear Charge, Z* Effective Nuclear Charge, Z* 17 18 ORBITAL BOX NOTATION for He, atomic number = 2 Arrows 2 depict electron spin 1s 1s One electron has n = 1, l = 0, m l = 0, ms = + 1/2 Other electron has n = 1, l = 0, m l = 0, ms = - 1/2 Page 3 See “Toolbox” for Electron Configuration tool. 19 20 Lithium Lithium Boron Boron Beryllium Beryllium Group 1A Atomic number = 3 1s22s1 ---> 3 total electrons 3p Group 2A Atomic number = 4 1s22s2 ---> 4 total electrons 3p 3p 3s 2p 2s 1s 3s 3s 2p 2p 2s 1s 22 23 Carbon Carbon 3p 3s 2p 2s 1s Group 3A Atomic number = 5 1s2 2s2 2p1 ---> 2s 2p 5 total electrons total 2s 1s 21 Group 4A Atomic number = 6 1s2 2s2 2p2 ---> 2s 2p 6 total electrons Here we see for the first time HUND’S RULE . When placing electrons in a set of orbitals having the same energy, we place them singly as long as possible. 24 Nitrogen Nitrogen 3p Oxygen Oxygen Group 5A Atomic number = 7 1s2 2s2 2p3 ---> 2s 2p 7 total electrons 3s 3p 3s 2p 2p 2s 2s 1s 1s Page 4 Group 6A Atomic number = 8 1s2 2s2 2p4 ---> 2s 2p 8 total electrons 25 26 Neon Neon Fluorine Fluorine Electron Configurations of p-Block Elements Group 8A Atomic number = 10 1s2 2s2 2p6 ---> 2s 2p 10 total electrons Group 7A Atomic number = 9 1s2 2s2 2p5 ---> 2s 2p 9 total electrons 3p 3p 3s 3s 2p 2p 2s 2s 27 Note that we have reached the end of the 2nd period, and the 2nd shell is full! 1s 1s 28 Sodium Sodium Group 1A Atomic number = 11 1s2 2s2 2p6 3s1 or 2s 2p 3s “neon core” + 3s 1 [Ne] 3s1 (uses rare gas notation) (uses Note that we have begun a new period. All Group 1A elements have [core]ns 1 configurations. 29 Group 5A Atomic number = 15 1s2 2s2 2p6 3s2 3p3 2s 2p 3s 3p [Ne] 3s2 3p3 3p Group 3A Atomic number = 13 1s2 2s2 2p6 3s2 3p1 2s 2p 3s 3p [Ne] 3s2 3p1 3p All Group 3A elements have [core] ns2 np1 np configurations where n is the period number. Page 5 30 Phosphorus Phosphorus Aluminum Aluminum 3p 3s 2p 2s 1s All Group 5A elements have [core ] ns 2 np3 np configurations where n is the period number. 3p 3s 2p 2s 1s 31 Calcium Calcium Group 2A Atomic number = 20 1s2 2s2 2p6 3s2 3p6 4s2 2s 2p 3s 3p [Ar] 4s2 All Group 2A elements have [core]ns2 configurations where n configurations is the period number. Transition Element Configurations 3d orbitals used for 3d orbitals used for Sc -- Zn (Table 8.4) Sc Zn (Table 8.4) Relationship of Electron Configuration and Region of the Periodic Table • • • • 32 Chromium 35 Lanthanides and Actinides Lanthanides and Actinides All these elements have the configuration [core] nsx (n - 1)dy (n - 2)fz (n and so are “f-block” elements. Cerium [Xe] 6s2 5d1 4f1 Uranium [Rn] 7s 2 6d1 5f3 Page 6 33 All 4th period elements have the configuration [argon] nsx (n - 1) dy and so are “d-block” elements. Gray = s block Orange = p block Green = d block Violet = f block 34 Transition Metals Transition Metals Table 8.4 Table 8.4 Iron Copper Lanthanide Element Configurations 4f orbitals used for 4f orbitals used for Ce -- Lu and 5f for Ce Lu and 5f for Th -- Lr (Table 8.2) Th Lr (Table 8.2) 36 Ion Configurations Ion Configurations 37 To form cations from elements remove 1 or more e- from subshell of highest n [or highest (n + l)]. P [Ne ] 3s2 3p3 - 3e- ---> P3+ [Ne] 3s2 3p0 Ion Configurations Ion Configurations 38 39 Ion Configurations Ion Configurations To form cations from elements remove 1 or more e- from subshell of highest n [or highest (n + l)]. P [Ne ] 3s2 3p3 - 3e- ---> P3+ [Ne] 3s2 3p0 For transition metals, remove ns electrons and then (n - 1) electrons. Fe [Ar] 4s2 3d6 loses 2 electrons ---> Fe 2+ [Ar ] 4s0 3d6 3p 3p 3s 3s 2p 2p 2s 2s 1s 1s 40 41 42 Ion Configurations Ion Configurations Ion Configurations Ion Configurations For transition metals, remove ns electrons and then (n - 1) electrons. For transition metals, remove ns electrons and then (n - 1) electrons. How do we know the configurations of ions? Determine the magnetic properties of ions. Determine magnetic Fe [Ar] 4s2 3d6 loses 2 electrons ---> Fe 2+ [Ar ] 4s0 3d6 Fe [Ar] 4s2 3d6 loses 2 electrons ---> Fe 2+ [Ar ] 4s0 3d6 Ions with UNPAIRED ELECTRONS are Ions UNPAIRED PARAMAGNETIC . Fe2+ Fe 4s 3d 4s 3d Fe2+ Fe 4s 3d 4s 3d Fe3+ 4s Page 7 3d Ion Configurations Ion Configurations Without unpaired electrons DIAMAGNETIC . Without DIAMAGNETIC ...
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This note was uploaded on 10/19/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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