Periodic Relationships Among the Elements

Transcription

1 Periodic Relationships Among the Elements Chapter 8 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Mendeleev s Periodic Table "...if all the elements be arranged in order of their atomic weights a periodic repetition of properties is obtained." - Mendeleyev

3 Dmitri Mendeleev Russian Invented periodic table Organized elements by properties Arranged elements by atomic mass Predicted existence of several unknown elements Element 101 Dmitri Mendeleev

4 Dmitri Mendeléev

5 Mendeleev s Periodic Table Group I II III IV V VI VII VIII Period 1 H=1 2 Li = 7 Be= 9.4 B = 11 C = 12 N = 14 O = 16 F = 19 3 Na = 23 Mg = 24 Al = 27.3 Si = 28 P = 31 S = 32 C = K = 39 Ca = 40? = 44 Ti = 48 V = 51 Cr = 52 Mn = 55 5 Cu = 63 Zn = 65? = 68? = 72 As = 75 Se = 78 Br = 80 6 Rb = 85 Sr = 87? Yt = 88 Zr = 90 Nb = 94 Mo = 96? = Ag = 108 Cd = 112 In = 113 Sn = 118 Sb = 122 Te = 125 J = Cs = 133 Ba = 137?Di = 138?Ce = 140 F = 19 Fe =56, Co = 59, Ni = 59 Ru= 104, Rh = 104, Pd = Os = 195, Ir = 197,

6 Mendeleev s Early Periodic Table REIHE N TABELLE II GRUPPE I RO K = RO 3 GRUPPE V GRUPPE VI RH3 R O5 2 RH2 RO 2 Cs = 133 Sr = 87? Yt = 88 Ba = 137 In = 113? Di = 138 (Au = 199) Si = 28 3? Er = 178 Tl= 204 V = 51 GRUPPE VII GRUPPE VIII RH R2O7 RO4? Ce = 140? La = 180 Te = 125 From Annalen der Chemie und Pharmacie, Pharmacie VIII, Supplementary Volume for 1872, p W = 184 Pd = 106, Ag = 108 U = 240 Ni = 59, Cu = 63 Ru = 104, Rh = 104, J = 127 Bi = 208 = 100 Ta = 182 Fe = 56, Co = 59, Br = 80 Mo = 96 Pb = 207 Mn = 55 Se = 78 Sb = 122 Cl = 35.5 Cr = 52 Nb = 94 Sn = 118 F = 19 S = 32 As = 75 Zr = 90 Th = 231 O = 16 P = 31 =?72 Hg = 200 N = 14 Ti = 48?= 68 Cd = 112 ( ) Al = 27.3 Zn = 65 (Ag = 108) C = 12?= 44 Ca = 40 Rb = 85 B = 11 Mg = 24 (Cu = 63) 9 10 RO 2 Be = 9.4 Na = RO Li = GRUPPE IV H=1 3 4 GRUPPE III RH GRUPPE II Os = 195, Ir = 197, Pt = 198, Au = 199

7 Elements Properties are Predicted Property Mendeleev s Predictions in 1871 Observed Properties Scandium (Discovered in 1877) Molar Mass Oxide formula Density of oxide Solubility of oxide 44 g M2O g Sc2O3 3.5 g / ml Dissolves in acids 3.86 g / ml Dissolves in acids Gallium (Discovered in 1875) Molar mass Density of metal Melting temperature Oxide formula Solubility of oxide 68 g 6.0 g / ml Low M2O g 5.96 g / ml 30 0C Ga2O3 Dissolves in ammonia solution Dissolves in ammonia Germanium (Discovered in 1886) Molar mass Density of metal Color of metal Melting temperature Oxide formula Density of oxide Chloride formula Density of chloride Boiling temperature of chloride 72 g 5.5 g / ml Dark gray High MO g 5.47 g / ml Grayish, white 900 0C GeO2 4.7 g / ml MCl g / ml GeCl4 1.9 g / ml Below 100 oc 1.89 g / ml 86 0C O Connor Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 119,

8 When the Elements Were Discovered 8

9 4f 5f 9 ns2np6 ns2np5 ns2np4 ns2np3 ns2np2 ns2np1 d10 d5 d1 ns2 ns1 Ground State Electron Configurations of the Elements

10 Classification of the Elements 10

11 Electron Configurations of Cations and Anions Of Representative Elements Na [Ne]3s1 Na+ [Ne] Ca [Ar]4s2 Ca2+ [Ar] Al [Ne]3s23p1 Al3+ [Ne] Atoms gain electrons so that anion has a noble-gas outer electron configuration. Atoms lose electrons so that cation has a noble-gas outer electron configuration. H 1s1 H- 1s2 or [He] F 1s22s22p5 F- 1s22s22p6 or [Ne] O 1s22s22p4 O2-1s22s22p6 or [Ne] N 1s22s22p3 N3-1s22s22p6 or [Ne] 11

12 Cations and Anions Of Representative Elements

13 Isoelectronic: have the same number of electrons, and hence the same ground-state electron configuration Na+: [Ne] Al3+: [Ne] O2-: 1s22s22p6 or [Ne] F-: 1s22s22p6 or [Ne] N3-: 1s22s22p6 or [Ne] Na+, Al3+, F-, O2-, and N3- are all isoelectronic with Ne What neutral atom is isoelectronic with H-? H-: 1s2 same electron configuration as He 13

14 Electron Configurations of Cations of Transition Metals When a cation is formed from an atom of a transition metal, electrons are always removed first from the ns orbital and then from the (n 1)d orbitals. Fe: [Ar]4s23d6 Fe2+: [Ar]4s03d6 or [Ar]3d6 Mn: [Ar]4s23d5 Mn2+: [Ar]4s03d5 or [Ar]3d5 Fe3+: [Ar]4s03d5 or [Ar]3d5 14

15 Effective nuclear charge (Zeff) is the positive charge felt by an electron. Zeff = Z - σ 0 < σ < Z (σ = shielding constant) Zeff Z number of inner or core electrons Z Core Zeff Radius (pm) Na Mg Al Si

16 Effective Nuclear Charge (Zeff) increasing Zeff increasing Zeff 16

17 Atomic Radii metallic radius covalent radius 17

18 18

19 Trends in Atomic Radii 19

20 Comparison of Atomic Radii with Ionic Radii 20

21 Cation is always smaller than atom from which it is formed. Anion is always larger than atom from which it is formed. 21

22 The Radii (in pm) of Ions of Familiar Elements 22

23 Chemistry in Action: The 3rd Liquid Element? 117 elements, 2 are liquids at 250C Br2 and Hg 223 Fr, t1/2 = 21 minutes Liquid? 23

24 Ionization energy is the minimum energy (kj/mol) required to remove an electron from a gaseous atom in its ground state. I1 + X (g) X+(g) + e- I1 first ionization energy I2 + X+(g) X2+(g) + e- I2 second ionization energy I3 + X2+(g) X3+(g) + e- I3 third ionization energy I1 < I2 < I3 24

25 25

26 Variation of the First Ionization Energy with Atomic Number Filled n=1 shell Filled n=2 shell Filled n=3 shell Filled n=4 shell Filled n=5 shell 26

27 General Trends in First Ionization Energies Increasing First Ionization Energy Increasing First Ionization Energy 27

28 Electron affinity is the negative of the energy change that occurs when an electron is accepted by an atom in the gaseous state to form an anion. X (g) + e- X-(g) F (g) + e- X-(g) H = -328 kj/mol EA = +328 kj/mol O (g) + e- O-(g) H = -141 kj/mol EA = +141 kj/mol 28

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30 Variation of Electron Affinity With Atomic Number (H Ba) 30

31 Group 1A Elements (ns1, n 2) M M+1 + 1e- 2M(s) + 2H2O(l) 2M2O(s) Increasing reactivity 4M(s) + O2(g) 2MOH(aq) + H2(g) 31

32 Group 1A Elements (ns1, n 2) 32

33 Group 2A Elements (ns2, n 2) M M+2 + 2e- Be(s) + 2H2O(l) Mg(s) + 2H2O(g) Mg(OH)2(aq) + H2(g) M(OH)2(aq) + H2(g) M = Ca, Sr, or Ba Increasing reactivity M(s) + 2H2O(l) No Reaction 33

34 Group 2A Elements (ns2, n 2) 34

35 Group 3A Elements (ns2np1, n 2) 4Al(s) + 3O2(g) 2Al(s) + 6H+(aq) 2Al2O3(s) 2Al3+(aq) + 3H2(g) 35

36 Group 3A Elements (ns2np1, n 2) 36

37 Group 4A Elements (ns2np2, n 2) Sn(s) + 2H+(aq) Sn2+(aq) + H2 (g) Pb(s) + 2H+(aq) Pb2+(aq) + H2 (g) 37

38 Group 4A Elements (ns2np2, n 2) 38

39 Group 5A Elements (ns2np3, n 2) N2O5(s) + H2O(l) P4O10(s) + 6H2O(l) 2HNO3(aq) 4H3PO4(aq) 39

40 Group 5A Elements (ns2np3, n 2) 40

41 Group 6A Elements (ns2np4, n 2) SO3(g) + H2O(l) H2SO4(aq) 41

42 Group 6A Elements (ns2np4, n 2) 42

43 Group 7A Elements (ns2np5, n 2) X2(g) + H2(g) X -1 2HX(g) Increasing reactivity X + 1e- 43

44 Group 7A Elements (ns2np5, n 2) 44

45 Group 8A Elements (ns2np6, n 2) Completely filled ns and np subshells. Highest ionization energy of all elements. No tendency to accept extra electrons. 45

46 Compounds of the Noble Gases A number of xenon compounds XeF4, XeO3, XeO4, XeOF4 exist. A few krypton compounds (KrF2, for example) have been prepared. 46

47 Comparison of Group 1A and 1B The metals in these two groups have similar outer electron configurations, with one electron in the outermost s orbital. Chemical properties are quite different due to difference in the ionization energy. Lower I1, more reactive 47

48 Properties of Oxides Across a Period basic acidic 48