03b electronic structure of atoms

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03b electronic structure of atoms

  1. 1. CHEM-111 General Chemistry Unit Three (b) Electronic Structure of Atoms by CHEMISTRY DEPARTMENT
  2. 2. The Electron Configurations of Elements Electron cloud Nucleus The Way the Electrons are Distributed Around the Nucleus of an Atom
  3. 3. ELECTRON CONFIGURATION IN SINGLE ATOM
  4. 4. Electrons exist in a number of cloud-like shell or energy levels ,one inside the other • The first innermost shell (n=1) ,K shell, is only small can hold one or two electrons . • The second energy level (n=2) is called the L Shell. • The third energy level, M shell corresponds to n=3. • The fourth energy level, the N shell ,corresponds to n=4 and so on.
  5. 5. Energy Levels and their Capacity of Electrons The maximum number of electrons in each shell = 2n2 No. of shell Name of shell Max. no. of electrons n = 1 K 2 x 12 = 2 n = 2 L 2 x 22 = 8 n =3 M 2 x 32 = 18 n = 4 N 2 x 42 = 32 (where n = number of shell)
  6. 6. Arrangement of Electrons in Energy Levels • Electrons are concentrated in certain region of space, called orbital. • Each shell contains different types and numbers of orbital. • Each orbital has different shape and energy. • Each orbital contains a maximum of two electrons.
  7. 7. Each shell contains different types and numbers of orbital Each orbital can have maximum of two electrons Shell Number (n) Shell name Name of Orbital in shells S p d f Total no. of electrons in different shell 1 K 1 0 0 0 2 2 L 1 3 0 0 8 3 4 M N 1 3 5 0 1 3 5 7 18 32
  8. 8. Sequence of Energy Levels for Atomic Orbital The sequence of energy-levels is important in determining the arrangement of electrons in an atom. This diagram is useful to determine which orbital in an atom are populated by electrons 1 s 2 s 2 p 3 s 3 p 4 s 3 d 4 p 5 s 4 d 5 p 6 s 4 f 5 d 6 p 7 s 5 f n = 7 n = 6 n = 5 n = 4 n = 3 n = 2 n =1 E N E R G Y
  9. 9. Each individual box represents an orbit An electron occupies the lowest energy orbital Sequence of Energy Levels for Atomic Orbital and Aufbau Principal E N E R G Y
  10. 10. Orbital and its Shapes Shape of s-Orbital Electron density is same regardless of direction spherical shape
  11. 11. Electron Density Distribution in the 1s, 2s and 3s Orbital of an Atom The nodes in the 2s and 3s orbits are actually empty spheres on which the electron density is zero. 3s2s1s 1s 2s 3s Node Orientation of s orbital
  12. 12. The shape of p orbital p orbital has 2 dumbbell-shaped lobes 2p The electron density is concentrated in two regions that lie on opposite sides of the nucleus, with their centers along a straight line that passes through the center of the atom.
  13. 13. Three different orientation (x,y,z) of p orbital around the nucleus z y x z y x z y x px orbita py orbital pz orbital Orientation of p orbital
  14. 14. Four orbital, dx2 -y2 , dxy, dyz, dxz, have same shape each with four lobes of electron density. dx2-y2 dxy dyz dxz dz2 Five different orientation of d-Orbitals The shape of dz2 is different
  15. 15. Li 1 1 H 2 3 He C 6 12 4 7 Be B C N O F Ne 4 5 6 7 8 9 10 9 11 12 1614 19 20 Na Mg Al Si P S Cl Ar 11 12 13 14 15 16 17 18 23 24 27 28 31 32 35.5 40 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 19 20 21 2223 24 25 26 27 28 29 35 3630 31 32 33 34 39 40 45 48 51 52 55 56 Rb Sr Y Zr NbMo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Ti Pb Bi Po At Rn Fr Ra Lr Rf Db Sg Bh Hs MtUunUuuUub UutUuq Uuh IA IIBIIIB IVB VIBVB VIIB VIIIB IB IIA IIIA IVA VA VIA VIIA VIIIA 1 2 3 4 5 6 7 8459 59 63.5 65 70 73 75 79 80 38 39 4037 41 42 43 44 4645 47 48 49 50 51 52 53 54 La Ce Pr NdPm Sm Eu Gd Tb Dy Ho ErTm Yb Ac Th Pa U Np PuAmCm Bk Cy EsFm Md No 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 89 88 90 91 92 93 94 95 96 97 98 99 101100 102 103 104 105 106 107 108 109 110 111 112 113 114 116 85.5 88 89 91 93 96 (98) 101 103 106 108 112 115 119 122 131 133 137 128 127 175 178.5 181 184 186 190 192 195 197 201 204 207 209 (209) (210) (222) (223) 226 (260) (261) (262) (263) (262) (265) (266) (269) (272) (277) (289) (289) 138 140 141 144 (145) 150 152 157 159 162.5 165 167 169 173 227 232 231 238 237 (244) (243) (247) (247) (251) (252) (257) (258) (259) Elements are arranged in increasing order of their atomic number Periodic Table of Elements
  16. 16. First shell Hydrogen 1 H Electronic Distribution of Elements of first three Periods Helium 2 He Second Shell Lithium 3 Li Beryllium 4 Be Boron 5 B Carbon 6 C Nitrogen 7 N Oxygen 8 O Fluorine 9 F Neon 10 Ne Third Shell Sodium 11 Na Magnesim 12 Mg Aluminum 13 Al Silicon 14 Si Phosphors 15 P Sulfur 16 S Chlorine 17 Cl Argon 18 Ar Periodic Table of Elements and Distribution of Electrons In Shells
  17. 17. Valence and Core Electrons Valence electrons Electrons located (in incompletely filled) outer shell, (main energy level) which take part in chemical reaction. Core electrons Electrons in shells below the outer shell are core electrons. Core electrons Valence electrons
  18. 18. How to write Electronic configuration of elements An unoccupied orbital represented by a line with orbital name written under it Hydrogen Helium S1 2S 2px y2p z 2p 1s2, 2s1 Lithium Beryllium Orbital Notation Li Examples 1s2 2s2 Be
  19. 19. ELECTRON CONFIGURATION OF FIRST 18 ELEMENTS Electron Configurations of 2nd Period Element Showing Two Notations Name Symbol 1s 2s 2p 2p 2p Electron configuration Lithium 3 Li - - - 1s2 2s1 Beryllium 4 Be - - - 1s2 2s2 Boron 5 B - - 1s2 2s2 2p1 Carbon 6 C - 1s2 2s2 2p2 Nitrogen 7 N 1s2 2s2 2p3 Oxygen 8 O 1s2 2s2 2p4 Fluorine 9 F 1s2 2s2 2p5 Neon 10 Ne 1s2 2s2 2p6
  20. 20. Electron Configurations of 3rd Period Elements Name Symbol 1s 2s 2p 3s 3p Nobel-gas notation Sodium 11 Na 2 2 6 1 - [Ne]3s1 Magnesium 12 Mg 2 2 6 2 - [Ne]3s2 Aluminum 13 Al 2 2 6 2 1 [Ne]3s2 3p1 Silicon 14 Si 2 2 6 2 2 [Ne]3s2 3p2 Phosphorus 15 P 2 2 6 2 3 [Ne]3s2 3p3 Sulfur 16 S 2 2 6 2 4 [Ne]3s2 3p4 Chlorine 17 Cl 2 2 6 2 5 [Ne]3s2 3p5 Argon 18 Ar 2 2 6 2 6 [Ne]3s2 3p6
  21. 21. Exercise 1. How many electrons are in shell 2 of the following elements? a) sodium b) nitrogen c) sulphur d) helium e) chlorine 2. Write the electron shell arrangement for each of the following elements. Example: sodium 2,8,1 a) carbon b) argon c) sulfur d) silicon. 3. Identify the elements that have the following electron shell arrangement. Energy Levels 1 2 3 a. 2 e - 1 e - b. 2 e- 8 e - 2 e - c. 1 e- d. 2 e- 8 e- 7 e -
  22. 22. Exercise 4.Name two elements which would exhibit physical and chemical behavior similar to chlorine. 5.What are the number of electrons in the outer energy level and the group number for each of the following elements.? a) Lithium b) silicon c) neon d) argon 1.The maximum number of electrons in d-orbital is: a) 2 b) 6 c) 10 d) 14 2. The electronic configuration of C is: a) 1s2 b) 1s2 , 2s1 c)1s2 , 2s2 , 2p2 12 6 M. C. Q:
  23. 23. 3. Indicate the sub shell having maximum 14 electrons: a) S orbital b) p orbital c) d orbital d) f orbital 4. Indicate the shell with n = 3 a) K b) L c) M d) N 5.The maximum number of electrons in M-shell is: a) 2 b) 8 c) 18 d) 32 6.The electrons of an atom are distributed ranging from higher to lower energy levels: a) True b) False

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