Periodic Properties Atomic & Ionic Radius Energy Electron Affinity We want to understand the variations in these properties in terms of electron configurations. The Periodic Table Elements in a column of the periodic table have very similar electron configurations. Elements in a column of the periodic table also have similar chemical properties. Valence electrons determine the chemical behavior of an atom. Valence Electrons Can you explain this graph? Valence electrons are those with the highest n value, plus any in partially filled d or f shells. These electrons are the farthest from the nucleus, and they have the highest energies. Thus they are the most accessible to other atoms. Valence Electrons Valence electrons are those with the highest n value, plus any in partially filled d or f shells. These electrons are the farthest from the nucleus, and they have the highest energies. Thus they are the most accessible to other atoms. Valence electrons determine the chemical properties of an atom. Paramagnetism Electrons have magnetic properties. Two electrons with opposite spins have opposite magnetic properties, so they cancel out each other s magnetism. Atoms with unpaired electrons are attracted or repelled by magnetic fields, and are said to be paramagnetic. This is a way to verify e configuration.
Atomic Radius Size of an atom is determined mainly by valence electrons. (Why?) Hard to define and measure Which would you expect to be larger: Na or K? N or F? Atomic Radius Variations Moving across a row, Z increases while valence electrons are added to the same n-shell size decreases Moving down a column, the n quantum number of the valence electrons increases size increases Ionic Radii Atomic Radius Variations Think about these the same way as for atoms: electron configurations. Be sure to use correct # of electrons. Which should be larger: Mg or Mg 2+? F or F? Ionic Radii Anions are always bigger than the corresponding neutral atom. Cations are always smaller than the corresponding neutral atom. For isoelectronic ions, the larger the nuclear charge, the smaller the ion.
Energy IE = amount of energy needed to remove an electron from a free neutral atom. Z + energy Z + + e Easy to measure (experiment similar to photoelectric effect) Energy How would you expect IE to vary as you go down a column of the Periodic Table?... as you go across a row? Why? Tell us the relative stabilities of different orbitals IE decreases going down a column of the periodic table. IE increases going across a row of the periodic table. Some exceptions: Filled shells or subshells are especially stable. Half-filled subshells are also fairly stable. Can you explain the general trends and the variations? Again? Again?
Higher Can also define and measure higher IE s: 2 nd IE: Z + + energy Z 2+ + e Can predict and understand these based on electron configuration of the ions involved. 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 2 nd 1st Energy 1st 2nd Energy Energy Li Be B C N O F Ne NaMg Al Si P S Cl Ar K Transition Metals - some complications Electron Attachment Enthalpy (Affinity) Measures atom s tendency to form anions EA = energy released upon adding an electron to a neutral atom, Z(g) + e Z (g) + energy (=EA) Older books called this the electron affinity, but is now called the Electron Attachment Enthalpy. This is opposite in sign from old definition. Note: EA can be positive or negative Electron Affinity If EA is negative, the atom wants to add an electron and form an anion. If EA is positive, the atom does not want to add an electron to form an anion. i.e., the anion is unstable. Which elements will have the most negative EA s? Why? Periodic Table: Metals & Non-metals What makes an element a metal or a non-metal? Properties? Electron configuration? How are metals & non-metals grouped in the periodic table?
Comments on the Periodic Table H Li Be Na Mg 0.9 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 0.9 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I 0.8 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 0.8 08 6.941 22.99 39.10 85.47 132.9 Fr Ra AcUnqUnpUnhUns (223) 1 3 11 19 37 55 87 9.012 24.30 40.08 87.62 137.3 (226) 4 12 20 38 56 88 44.96 88.91 138.9 (227) 21 39 57 89 1.4 47.88 92 178.5 22 40 72 104 1.4 Lanthanide series Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 50.94 92.91 180.9 140.1 58 59 60 61 62 63 64 65 66 67 68 69 70 140.9 144.2 (145) 150.4 152.0 Actinide series Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 232.0 23 41 73 105 90 52.00 95.94 183.8 23 Metals 91 24 42 74 106 54.94 (98) 186.2 (261) (262) (263) (262) 238.0 92 25 43 75 107 55.85 10 190.2 (237) 93 26 44 76 Zintl Line (fuzzy) 58.93 102.9 192.2 (244) 27 45 77 58.69 106.4 195.1 157.2 158.9 16 94 95 96 97 98 99 100 101 102 (243) 28 46 78 63.55 107.9 197.0 (247) 29 47 79 65.39 112.4 200.6 (247) 30 48 80 2.0 B 10.81 Al 26.98 69.72 114.8 204.4 (251) Nonmetals 5 13 31 49 81 C 12.01 Si 28.09 72.61 118.7 207.2 164.9 (252) 6 14 32 50 82 3.0 N 14.01 P 30.97 74.92 12 209.0 167.3 (257) 7 15 33 51 83 3.5 2.4 O 16.00 S 32.07 78.96 127.6 (209) 168.9 (258) 8 16 34 52 84 4.0 3.0 2.8 F 19.00 Cl 35.45 79.90 126.9 (210) 173.0 (259) 9 17 35 53 85 He 4.003 Ne 20.18 Ar 39.95 83.80 Xe 13 (222) 175.0 (260) 71 10 18 36 54 86 103 2