Lecture 7 Periodic properties Read BLB 2 5 7 1 7 6 HW BLB 2 37 7 11 23 25 27 31 45a c 47a e f 53 61 94 Sup 7 1 12 Know screening effects periodic properties atomic and ion sizes isoelectronic series electron configurations of ions ionization energies electron affinities Exam 1 Monday Feb 9 6 30 start preparing now only nontext programmable calculators are allowed no PDAs blackberries cell phones etc will be permitted Bring pencils student ID and a calculator Absolutely NO text programmable calculators or wireless devices will be checked Form a study group use the CRC take advantage of SI info on web use the online resources and work those problems practice practice practice Bonus deadline for Skill check tests 3 4 is tomorrow Thursday 1 29 midnight Bonus deadline for Skill check test 5 is Thursday 2 5 Skill check test 6 is SUNDAY 2 8 Sheets s office hours Mondays 12 30 2 Tuesdays 10 30 12 in 324 Chem or 326 Chem Sheets Page 1 Lecture 7 Key to understanding periodic trends As n atomic orbitals become less stable As Z protons any given orbital becomes more stable Zeff Trade off Z e attraction e e repulsion recall Coulomb s Law Q1Q2 E d column group or family row period Sheets Page 2 Lecture 7 Electron configuration the periodic table electron configuration determines 1 periodic table organization Chap 6 2 properties of the elements atomic size ionization energy electron affinities reactivity properties of elements determined by n of orbitals and atomic z nuclear charge valence shell configuration is key to element s properties valence e determine the chemistry of an element core electrons smaller radius lower E mostly not participating in chemistry of reactions Sheets Page 3 Lecture 7 Atomic size Screening again see p 3 ff of Lecture 5 notes Zeff Z S weak screening by e with same n S is average number of e between nucleus e of interest often but not always use number of core e Sheets Page 4 Lecture 7 Ion sizes What is happening when we make a cation or anion cations are why than parent atoms anions are why than parent atoms atom sizes ion sizes also going down family Sheets Page 5 Lecture 7 Isoelectronic series isoelectronic same number of e same e configuration example 10 e each He 2s22p6 Z 8 9 O2 F 10 Ne 11 12 Na Mg2 13 Al3 Zeff size For this example Zeff Z 2 from He Sheets Page 6 Lecture 7 Makin ions to form a cation remove e first from orbitals with highest n these are the valence e in transition metals TM s electrons are part of valence e Ag Kr 5s14d10 Ag Kr 4d10 when forming TM ions remove e first then maybe remove e if needed ions with different charges may be formed Fe Fe2 Fe3 Ar 4s23d6 Ar 3d6 Ar 3d5 to form an anion add e to empty or partially filled orbital with available n Sheets Page 7 Lecture 7 Ionization energy IE n energy to remove 1 e in the gas phase n I1 first ionization energy IE M g M g e E I1 I2 second ionization energy M g M2 g e E I2 In 0 therefore energy is endothermic Sheets Page 8 Lecture 7 Ionization energy IE I1 kJ mol Na 495 Mg 738 Al 578 Si 786 P S Cl Ar 1012 1000 1251 1521 e closer to nucleus more difficult to remove as atomic size IE therefore IE left to right exceptions extra energy to remove e from filled subshells Mg Ar or from half filled subshell P Sheets Page 9 Lecture 7 Electron affinity EA energy to add 1 e in the gas phase M g e M g E EA EA either endothermic E energetically unfavorable or exothermic E energetically favorable EA of cation is always exothermic E because opposite process of IE M g e M g EA M I1 M complex property due to trade off between Sheets Z e attraction e e repulsion Page 10 Lecture 7 Electron affinity trends most negative energetically favorable for halogens group 7A why group 2A Be Mg Ca do not want to fill a new subshell have positive values energetically unfavorable for EA unstable negative ions group 1A Li Na K negative ions are not stable but have ns2 configuration noble gases group 8A have positive values for EA Sheets Page 11 why Lecture 7 Review of periodic trends atomic size ionization energy electron affinity both and group 7A most negative metallic character metals lose e oxidation nonmetals gain e reduction Sheets Page 12 Lecture 7 The modern periodic table elements listed in order of increasing atomic number Z elements in same column group or family have similar chemical properties metals toward left side of PT reactivity going down group most metallic character lower left of PT nonmetals toward right side of PT reactivity upward most nonmetallic character upper right of PT noble gases at far right of PT quite inert Sheets Page 13 Lecture 7 Metals chemistry of metals form group 1A alkali 1 cations on atom valence e ns1 most active Cs Fr group 2A alkaline earth 2 cations on atom valence e ns2 less reactive than group 1A transition 1 2 3 cations reactivity as IE easier to lose that e as n Sheets Page 14 Lecture 7 Nonmetals group 8A noble gases on atom valence e ns2np6 almost completely inert except XeFn all gases chemistry of nonmetals form group 7A halogens 1 anions on atom valence e ns2np5 most reactive nonmetals particularly F2 reactions dominated by X2 2e 2X reactivity of halogens as EA group 6A oxygen family 2 anions on atom valence e ns2np4 Sheets Page 15 Lecture 7 Nonmetals cont compounds which are entirely nonmetals are usually compounds CO2 hydrocarbons seven diatomics H2 N2 O2 F2 Cl2 Br2 I2 why will see in Chap 8 compounds metal nonmetal are compounds 2 Al s 3 Br2 l 2 AlBr3 s Sheets Page 16 Lecture 7 Before next class Read BLB 2 6 2 8 8 1 8 4 HW BLB 2 51 53 57 59 65 67 8 16 22 25 29 37 39 Sup 2 4 Know chemical bonding ionic bonding covalent bonding metallic bonding Lewis symbols lattice energy Sheets Page 17 Lecture 7
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