Pultz 1. Test # 1 on F 14 Sept 2012 over Chapter 8 and 9

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1 Test # 1 on F 14 Sept 2012 over Chapter 8 and 9 Pultz 1 Order for writing orbitals for ground state electron configuration for Sc and higher atomic numbers: Sc: [Ar] 3d 1 4s 2 or [Ar]4s 2 3d 1 Both are correct. First order groups together all subshells with same principal quantum number and better represents the order in which electrons are lost when an atom ionizes. Second order fits better to the typical order in which orbitals fill. Additional problems for test # 1 Chapter 8 Exercises #3, 5, 19, 25, 30, 33, 43, 51, 75, 83 Concept Assessments on p346 and p352 and p356 Practice Examples 9-1 through 9-3 Chapter 9 Exercises #17 and Arrange Na, Mg, and K in order of increasing first ionization energy. (a) K < Na < Mg (b) K < Mg < Na (c) Na < Mg < K (d) Mg < Na < K (e) Mg < K < Na 2. An element has the following successive ionization energies (in kj/mol): I I I I I The element is (a) B (b) Be (c) C (d) Li (e) N S&TY Which atom has the smallest first ionization energy? Be B C N Which atom has the smallest first ionization energy? N O F Ne Which atom has the largest first ionization energy? Li Be B Which atom has the largest first ionization energy? B C N O Which atom has the largest first ionization energy? Li Na K Rb Cs 4. Choose the electron configuration that corresponds to an excited state. (a) [Ar]3d 3 4s 2 (b) [Kr]5s 1 (c) [Ar]3d 5 4s 1 (d) [Ne]3s 1 3p 6 (e) [Xe]4f 14 5d 10 6s 2 ANSWER KEY 1. Arrange Na, Mg, and K in order of increasing first ionization energy. (a) K < Na < Mg (b) K < Mg < Na (c) Na < Mg < K (d) Mg < Na < K (e) Mg < K < Na 2. An element has the following successive ionization energies (in kj/mol): I I I I I The element is (a) B (b) Be (c) C (d) Li (e) N S&TY B O Be N Li 4. Choose the electron configuration that corresponds to an excited state. S&TY8.4 (a) [Ar]3d 3 4s 2 (b) [Kr]5s 1 (c) [Ar]3d 5 4s 1 (d) [Ne]3s 1 3p 6 (e) [Xe]4f 14 5d 10 6s 2 Problems for final exam: Chapter 5, p173 #65-67, #65: An iron ore sample weighing g is dissolved in HCl(aq), and the iron is obtained as Fe 2+ (aq). This solution is then titrated with ml of M K 2Cr 2O 7(aq), producing Fe 3+ and Cr 3+. Calculate the mass percent Fe in the ore sample.

2 9-1 Periodic Table is way of organizing physical and chemical properties of elements Pultz 2 The basis of the Periodic Table is the electron configurations of the elements, so we can also use the Periodic Table to help remember the electron configurations of the elements. In 1869 Mendeleev and Meyer independently proposed the periodic law: When elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically. Meyer looked at molar volume Figure 9-1 Mendeleev's insight was to leave spaces for undiscovered elements and correct some atomic massestable 9-1 Moseley used X-ray spectra to determine nuclear charge ==> atomic number modern periodic table: s block & p block for main group elements d block for transition metals; f block for inner transition elements Figure Metals, metalloids, and nonmetals and ions Most metals are good conductors of heat and electricity, are malleable and ductile, and are solid at 25 C, except Hg is liquid. Nonmetals tend to be poor conductors of heat and electricity (except graphite electrodes) and are either brittle solids or gases or Br 2 (l). Metalloids Going across a row, properties of main group elements change significantly since electron configuration changes significantly. Going across a row, properties of transition elements change some since electron configuration primarily changes one level in (in 4th row, usually just change number of 3d electrons and keep two 4s electrons). Within the Lanthanide or Actinide series, the number of electrons in the 4f or 5f subshell changes, and this is two levels in from the outermost electrons in the 6s or 7s orbital; thus these elements are very similar Noble gas electron configuration is particularly unreactive. Metal atoms tend to lose electrons in order to obtain the nearest noble gas electron configuration. Nonmetal atoms tend to gain electrons in order to obtain the nearest noble gas electron configuration. Except for Al, the metals in groups 13, 14, 15, and 16 do not truly obtain a noble gas electron configuration because they keep their d electrons (and any f electrons) added since the preceding noble gas. Another complication for metals in groups 13, 14, 15, and 16 is that the s valence electrons are often not lost, especially for heavier metals. Tl + and Pb 2+ and Bi 3+ are more common than their higher charged ions. Electron configurations for: Cs + Ba 2+ Br - Se 2- Charge on transition metal ions is often unpredictable. Electron configuration for Sc 3+, Ti 2+ and Ti 3+ and Ti 4+, Fe 2+ and Fe 3+, Cu + and Cu 2+

3 Pultz Sizes of atoms and ions and periodic trends Atomic radii also called covalent atomic radii because it is calculated from measurement of distance between nuclei in covalent bonds (Cl 2, diamond, etc.) Figure 9-3 is only an estimate since orbitals decay exponentially Trends & explain Atomic radii decrease going L to R across a period Figure 9-4 Atomic radii increase going down a group usually Figure 9-8 For transition elements within a period, Z eff constant atomic size vs. cation size Figure 9-6 atomic size vs. anion size Figure 9-7 For isoelectronic ions, the higher the charge, the smaller the ion: O 2- F - Na + Mg Ionization energy energy required to remove e - from gaseous atom/ion in ground state depends on F q 1 q 2 /r 2 = ez eff /r 2 Z eff = effective nuclear charge depends on n & l First Ionization Energies Figure 12.35: Ionization energy Figure 9-9 (note Ga & Hg) or Zumdahl 4 th (every element shown) Copyright by Houghton Mifflin Company. All rights reserved. Note trends and effect of changing l or pairing electrons

4 U&B 2 nd edition Pultz 4

5 PHHM9 Table 9-4 or Umland&Bellama2nd (more extensive & doesn t stop with 1 st core electron) Pultz 5 Choose an element & look at successive I.E. 1st vs 2nd vs 3rd ionization energies ==> Probable monatomic ions

6 Pultz 6 Umland&Bellama2nd Electron configurations of ions: K +, Cl -, Mn 2+, Cu +, In + form cations by removing electrons from orbital with highest n 9-5 Electron affinity: Cl(g) + e - (g) Cl - (g) gaseous atom gains electron When a gaseous halogen atom gains an electron, the reaction is highly exothermic. no clear trends Figure 9-10 confusion arising from two sign conventions; no questions except for definition

7 Pultz Magnetic properties Property magnetic field electron spins effect diamagnetic repelled by paired individual paramagnetic attracted by unpaired individual ferromagnetic attracted by unpaired bulk work Practice Example 9-4A on p Trends in Periodic Table Figure 9-8 shows sizes of atoms & ions; Ga atom is exception First ionization energies: Prose on p. 359 and Figure 9-11 over-simplify Ignore electron affinity in Figure 9-11 Metallic character in Figure 9-11 correlates to low electronegativity Assume that properties change uniformly from top to bottom of a group of elements in the periodic table, for lack of better knowledge. Use this assumption in Example 9-5 on p360. But top element in column of the periodic table is often different from the rest: H is nonmetal vs alkali metals; Be(OH) 2 can act as an acid and a base; B is nonmetal; HF is weak acid, but HCl & HBr & HI are strong acids. Often have diagonal relationships! Li Be B Mg Al Si correlates to electronegativity correlates to ion size correlates to atomic size correlates to charge/size ratio Be(OH) 2 [+2/31pm =.06] & Al(OH) 3 [+3/50pm =.06] are both amphoteric; Mg(OH) 2 [+2/65pm =.03] is basic B(OH) 3 and Si(OH) 4 and As(OH) 3 are acidic; Be(OH) 2 and Al(OH) 3 and Sb(OH) 3 are amphoteric. Note peak in melting points for third-period elements Figure 9-13 Acid-Base nature of element oxides Li 2 O(s) + HOH(l) 2 Li + (aq) + 2 OH - (aq) CaO(s) + HOH(l) Ca 2+ (aq) + 2 OH - (aq) Moving down a column, the elements become more metallic and their oxides become more basic. SO 3 (g) + HOH(l) H 2 SO 4 (aq) Moving left to right in a period, elements become less metallic and their oxides become more acidic. Amphoteric: a substance that can act as a Br/onsted base and as a Lewis acid. ( 16-9) Al(OH) 3 (s) + 3 H + (aq) Al 3+ (aq) + 3 H 2 O(l) Al(OH) 3 (s) + :OH - (aq) [Al(OH) 4 ] - (aq) as a Br/onsted base as a Lewis acid pages 363 and A-33 have inadequate definition for amphoteric Figure 9-17 shows acidic, basic and amphoteric oxides of main group elements