Chapter 08 Periodic Trends

Transcription

1 Chempocalypse Now! Chapter 08 Periodic Trends Page 1 Chapter 08 Periodic Trends Topics 03 and 13 from the IB HL Chemistry Curriculum 3.1 The periodic table (1 Hour) Assessment Statement Obj Teacher s Notes Describe the arrangement of elements in the periodic table in order of increasing atomic number. 2 Names and symbols of the elements are given in the Chemistry data booklet. The history of the periodic table will not be assessed. TOK: The predictive power of Mendeleev s periodic table could be emphasized. He is an example of a scientist as a risk taker Distinguish between the terms group and period. 2 The numbering system for groups in the periodic table is shown in the Chemistry data booklet. Students should also be aware of the position of the transition elements in the periodic table Apply the relationship between the electron arrangement of elements and their position in the periodic table up to Z = Apply the relationship between the number of electrons in the highest occupied energy level for an element and its position in the periodic table. 2 99M110 In which region of the Periodic Table would the element with the electronic structure below be located? 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 6 5s 2 A. Group 6 B. Noble gases C. s block D. d block 03M106 Which is related to the number of electrons in the outer main energy level of the elements from the alkali metals to the halogens? I. Group number II. Period number A. I only B. II only C. Both I and II D. Neither I nor II

2 Chempocalypse Now! Chapter 08 Periodic Trends Page 2 Use the Periodic Table to identify the position of the following elements. Element Period Group Helium Chlorine Barium Francium Phosphorus is in Period 3 and Group 5 of the Periodic Table. (a) Distinguish between the terms period and group. (b) State the electron arrangement of phosphorus and relate it to its position in the Periodic Table. How many valence (outer shell) electrons are present in the atoms of the element with atomic number 51?

3 Chempocalypse Now! Chapter 08 Periodic Trends Page Physical properties (2 Hours) Assessment Statement Obj Teacher s Notes Define the terms first ionization energy and electronegativity Describe and explain the trends in atomic radii, ionic radii, first ionization energies, electronegativities and melting points for the alkali metals (Li Cs) and the halogens (F I). 3 Data for all these properties is listed in the Chemistry data booklet. Explanations for the first four trends should be given in terms of the balance between the attraction of the nucleus for the electrons and the repulsion between electrons. Explanations based on effective nuclear charge are not required Describe and explain the trends in atomic radii, ionic radii, first ionization energies and electronegativities for elements across period 3. 3 Aim 7: Databases and simulations can be used here Compare the relative electronegativity values of two or more elements based on their positions in the periodic table. 3 98N109 Which one of the following series of atomic or ionic radii is NOT arranged in order of increasing size? A. Li, Na, K B. Na, Mg, Al C. Cl, Br, I D. F, O 2, N 3 01M102 The reason for the general increase in ionization energy of the elements across period 3 of the Periodic Table is the increasing number of A. Outer electrons B. Neutrons C. Protons D. Electron sub-levels occupied

4 Chempocalypse Now! Chapter 08 Periodic Trends Page 4 99N106 Values for the first ionization energies (IE) for five successive elements in the Periodic Table are given below. Based on these values, which statement is correct? Element K L M N O P IE (kj mol 1 ) ? A. The outermost electron in element K is in a higher energy level than that in element L B. Element M is probably a metal C. Element N is probably a non-metal D. Element P has a lower first ionization than element O 98M108 All of the following factors affect the value of the ionization energy of an atom except the A. Mass of the atom. B. Charge on the nucleus. C. Size of the atom. D. Main energy level from which the electron is removed. 97N103 Which of the following elements would have the largest second ionization energy? A. Ne B. Na C. Mg D. Al 05N111 Which statement about electronegativity is correct? A. Electronegativity decreases across a period. B. Electronegativity increases down a group. C. Metals generally have lower electronegativity values than non-metals. D. Noble gases have the highest electronegativity values.

5 Chempocalypse Now! Chapter 08 Periodic Trends Page 5 01N111 As the size of the halogen molecules, X 2, increases down the group, their boiling points A. decrease due to decreasing electronegativity. B. decrease due to decreasing bond energies. C. increase due to increasing permanent dipole-dipole attraction. D. increase due to increasing van der Waals forces. 03N107 Which properties of period 3 elements increase from sodium to argon? I. Nuclear charge II. Atomic radius III. Electronegativity A. I and II only B. I and III only C. II and III only D. I, II, and III 99N108 Which property of alkali metals changes as stated with increasing atomic number? A. Atomic radius decreases B. Reactivity with water decreases C. Electronegativity increases D. Melting point decreases Explain what is meant by the atomic radius of an element.

6 Chempocalypse Now! Chapter 08 Periodic Trends Page 6 The atomic radii of the elements are found in Table 8 of the IB Data book. (i) Explain why no values for atomic radii are given for the noble gases. (ii) Describe and explain the trend in atomic radii across the Period 3 elements. Explain why sulfur has a higher melting point than phosphorus. Which physical property generally increases down a group but decreases from left to right across a period? A. melting point B. electronegativity C. ionization energy D. atomic radius The elements in the Periodic Table are arranged in order of increasing: A. relative atomic mass B. ionic radii C. nuclear charge D. ionization energy What is the order of decreasing radii for the species Cl, Cl 1+, and Cl 1? Which one of the following elements has the highest electronegativity? A. Be B. Cl C. Ca D. Br

7 Chempocalypse Now! Chapter 08 Periodic Trends Page Chemical properties (2 Hours) Assessment Statement Obj Teacher s Notes Discuss the similarities and differences in the chemical properties of elements in the same group. 3 The following reactions should be covered. Alkali metals (Li, Na and K) with water Alkali metals (Li, Na and K) with halogens (Cl 2, Br 2, and I 2 ) Halogens (Cl 2, Br 2 and I 2 ) with halide ions (Cl, Br, and I ) Discuss the changes in nature, from ionic to covalent and from basic to acidic, of the oxides across period 3. 3 Equations are required for the reactions of Na 2 O, MgO, P 4 O 10 and SO 3 with water. Aim 8: Non-metal oxides are produced by many large-scale industrial processes and the combustion engine. These acidic gases cause large-scale pollution to lakes and forests, and localized pollution in cities. 02N107 Which of the following displacement reactions is possible? A. Br 2 (aq) + 2Cl (aq) 2Br (aq) + Cl 2 (aq) B. I 2 (aq) + 2Cl (aq) 2I (aq) + Cl 2 (aq) C. Cl 2 (aq) + 2I (aq) 2Cl (aq) + I 2 (aq) D. I 2 (aq) + 2Br (aq) 2I (aq) + Br 2 (aq) 02M110 Which of the following reactions is/are spontaneous? I. Cl 2 + 2Br 2Cl + Br 2 II. Br 2 + 2I 2Br + I 2 A. I only B. II only C. Both I and II D. Neither I nor II State two observations you could make during the reaction between sodium and water. Give an equation for the reaction. How do the reactivities of the alkali metals and the halogens vary down the group?

8 Chempocalypse Now! Chapter 08 Periodic Trends Page 8 03N108 Which general trends are correct for the oxides of the period 3 elements (Na 2 O to Cl 2 O)? I. Acid character decreases. II. Electrical conductivity (in the molten state) decreases. III. Bonding changes from ionic to covalent. A. I and II only B. I and III only C. II and III only D. I, II, and III Which property of the halogens increases from fluorine to iodine? A. ionic charge B. electronegativity C. melting point of the element D. chemical reactivity with metals. An oxide of a Period 3 element is solid at room temperature and forms a basic oxide. Identify the element. A. Mg B. Al C. P D. S Which pair of elements has the most similar chemical properties? A. N and S B. N and P C. P and Cl D. N and Cl Identify the oxide which forms an acidic solution when added to water. A. Na 2 O(s) B. MgO(s) C. SiO 2 (s) D. SO 2

9 Chempocalypse Now! Chapter 08 Periodic Trends Page 9 Use the data below to identify the state or the four oxides listed under standard conditions. Oxides Melting Point (K) Boiling Point (K) MgO SiO 2 (quartz) P 4 O SO Explain the difference in melting points by referring to the bonding and structure in each case. The oxides are added to separate samples of pure water. State whether the resulting liquid is acidic, neutral or alkaline. Describe all chemical reactions by giving chemical equations. Use a chemical equation to describe the reaction of aluminum oxide with hydrochloric acid. Use a chemical equation to describe the reaction of aluminum oxide with sodium hydroxide.

10 Chempocalypse Now! Chapter 08 Periodic Trends Page Trends across period 3 (2 Hours) Assessment Statement Obj Teacher s Notes Explain the physical states (under standard conditions) and electrical conductivity (in the molten state) of the chlorides and oxides of the elements in period 3 in terms of their bonding and structure. 3 Include the following oxides and chlorides: Oxides: Na 2 O, MgO, Al 2 O 3, SiO 2, P 4 O 10, SO 2 and SO 3, Cl 2 O and Cl 2 O 7 Chlorides: NaCl, MgCl 2, Al 2 Cl 6, SiCl 4, PCl 3 and PCl 5, and Cl Describe the reactions of chlorine and the chlorides referred to in with water. 2 97M122 Which of the following substances is a poor electrical conductor in the solid state but a good conductor in the liquid state? A. Paraffin B. Silicon dioxide C. Sodium D. Sodium fluoride 04M107 Which of the following oxides is (are) gas(es) at room temperature? I. SiO 2 II. P 4 O 6 III. SO 2 A. I only B. III only C. I and II only D. II and III only

11 Chempocalypse Now! Chapter 08 Periodic Trends Page 11 Usethe data below to identify the states of the four chlorides listed under standard conditions of temperature (298 K) and pressure (100 kpa). Oxides Melting Point (K) Boiling Point (K) NaCl AlCl sublimes SiCl PCl Explain the difference in melting points by referring to the bonding and structure in each case. The chlorides are added to separate samples of pure water. State whether the resulting liquid is acidic, neutral or alkaline. Describe all chemical reactions by giving chemical equations.

12 Chempocalypse Now! Chapter 08 Periodic Trends Page First-row d-block elements (2 Hours) Assessment Statement Obj Teacher s Notes List the characteristic properties of transition elements. 1 Examples should include variable oxidation number, complex ion formation, existence of colored compounds, and catalytic properties Explain why Sc and Zn are not considered to be transition elements Explain the existence of variable oxidation number in ions of transition elements. 3 Students should know that all transition elements can show an oxidation number of +2. In addition, they should be familiar with the oxidation numbers of the following: Cr (+3, +6), Mn (+4, +7), Fe (+3), and Cu (+1) Define the term ligand Describe and explain the formation of complexes of d-block elements Explain why some complexes of d-block elements are colored State examples of the catalytic action of transition elements and their compounds. 3 Include [Fe(H 2 O) 6 ] 3+,[Fe(CN) 6 ] 3,[CuCl 4 ] 2, and [Ag(NH 3 ) 2 ] +. Only monodentate ligands are required. 3 Students need only know that, in complexes, the d sub-level splits into two sets of orbitals of different energy and the electronic transitions that take place between them are responsible for their colors. 1 Examples should include: MnO 2 in the decomposition of hydrogen peroxide V 2 O 5 in the Contact process Fe in the Haber process and in heme Ni in the conversion of alkenes to alkanes Co in vitamin B 12 Pd and Pt in catalytic converters The mechanisms of action will not be assessed. 01N109 Fe(H 2 O) 3+ 6 (aq) + 6 CN 1 (aq) Fe(CN) 3 6 (aq) + 6 H 2 O(l) In the equation above, the cyanide ions act as A. Bronsted bases. B. Lewis acids. C. Ligands D. Reducing agents. 01M123 Which could not act as a ligand in a complex ion of a d-block element? A. Cl B. NCl 3 C. PCl 3 D. PCl 5

13 Chempocalypse Now! Chapter 08 Periodic Trends Page 13 00N110 Which aqueous complex ion will not be colored? A. Ni 2+ B. Fe 2+ C. Sc 3+ D. Cr 3+ 02N110 Consider the following coordination compounds I. [Pt(NH 3 ) 4 ]Cl 2 II. [Pt(NH 3 ) 4 Cl]Cl III. [Pt(NH 3 ) 4 Cl 2 ] What are the charges on the complex ions? I II III A B C D M142 Which one of the following compounds is most likely to be colored and paramagnetic? A. KBr B. NiSO 4 C. Ca(NO 3 ) 2 D. Pb(C 2 H 3 O 2 ) 2 98M110 The colors of the compounds of d-block elements are due to electron transitions A. Between different d orbitals. B. Between d orbitals and s orbitals. C. Among the attached ligands. D. From the metal to the attached ligands.

14 Chempocalypse Now! Chapter 08 Periodic Trends Page 14 State the electron configuration of the following metal ions by filling in the boxes below. Use arrows to represent the electron spin. Ion 3d 4s Sc 3+ Ti 3+ Ni 2+ Zn 2+ Identify the property/properties which are characteristic of an element found in the d block of the Periodic Table. A. All the compounds of the element are ionic. B. The element exhibits a variety of oxidation states and colors in its compounds. C. The element has a low melting point. D. The element is a good conductor of heat and electricity. Identify the oxidation number which is the most common among the first row transition elements A. +1 B. +2 C. +4 D. +6 An element has the electronic configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 3. Which oxidation state(s)would this element show? A. + 2 and + 3 only B. +2 and +5 only C. +3 and +5 only D. +2,+3,+4 and +5 State the full electron configuration of scandium (Sc). State the full electron configuration of Sc 3+ Explain why scandium is not classed as a transition metal. State the oxidation states shown by calcium and chromium, and explain the difference in their behavior.

15 Chempocalypse Now! Chapter 08 Periodic Trends Page 15 Identify the species which cannot act as a ligand: A. H 2 O B. CO C. CH 4 D. Cl Consider the reaction below: [Cu(H 2 O) 6 ] 2+ (aq) + 4 HCl(aq) [CuCl 4 ] 2 (aq) + 6 H 2 O(aq) + 4H + (aq) Which of the following is acting as a ligand? A. H + only B. H + and Cl only C. H 2 O and Cl only D. H +, H 2 O and Cl The color and formula of some coordination compounds of hydrated forms of chromium (III) chloride are listed in this table: What are the charges on each of the complex ions? Formula Color I [Cr(H 2 O) 6 ]Cl 3 Purple II [CrCl(H 2 O) 5 ]Cl 2 H 2 O Blue-green III [CrCl 2 (H 2 O) 4 ]Cl 2H 2 O Green I II III A B C D Explain why the two cobalt complex ions [Co(H 2 O) 6 ] 2+ and [CoCI 4 ] 2 are different colors.

16 Chempocalypse Now! Chapter 08 Periodic Trends Page 16 Study the structure of heme shown in the photograph on page 103 of your IB textbook. (a) What is the oxidation state of the central iron ion? (b) What is geometry of the nitrogen atoms around the central iron ion? (c) Explain why the complex is ideally suited to carry oxygen around the body. Name the catalyst in each of the following processes: (a) The hydrogenation of vegetable oils to form margarine: R 1 CH=CH R 2 + H 2 R 1 CH 2 CH 2 R 2 (b) The manufacture of sulfuric acid in the Contact process. (c) The removal of carbon and nitrogen monoxide from exhaust emissions. Distinguish between homogeneous and heterogeneous catalysis. Explain why the transition metals make effective heterogeneous catalysts. Explain why heterogeneous catalysts are generally used in industrial processes.

17 Chempocalypse Now! Chapter 08 Periodic Trends Page 17 Chapter 08 Review Questions: For which element are the group number and the period number the same? A. Li B. Be C. B D. Mg Which properties of Period 3 elements increase from sodium to argon: I. nuclear charge II. atomic radius III. electroneqativity? A. I and II only B. I and III only C. II and III only D. I,ll and III Which pair of elements reacts most readily? A. Li + Br 2 B. Li + Cl 2 C. K + Br 2 D. K + Cl 2 Which of the reactions below occur as written? I. Br I 2 Br + I 2 II. Br Cl 2 Br + Cl 2 A. I only B. II only C. both I and II D. neither I nor II

18 Chempocalypse Now! Chapter 08 Periodic Trends Page 18 Explain the following statements. (a) The first ionization energy of sodium is: (i) less than that of magnesium. (ii) greater than that of potassium. (b) The electronegativity of chlorine is higher than that of sulfur. Describe the acid-base character of the oxides of the Period 3 elements Na to Ar. For sodium oxide and sulfur trioxide, write balanced equations to illustrate their acid-base character. Atomic radii and ionic radii are found in the IB Data booklet. Explain why: (a) the magnesium ion is much smaller than the magnesium atom. (b) there is a large increase in ionic radius from silicon to phosphorus. (c) the ionic radius of Na + is less than that of F.

19 Chempocalypse Now! Chapter 08 Periodic Trends Page 19 Classify each of the following oxides as acidic, basic or amphoteric. (i) (ii) (iii) aluminium oxide sodium oxide sulfur dioxide Write an equation for each reaction between water and (i) sodium oxide (ii) sulfur dioxide State and explain the trends in the atomic radius and the ionization energy (a) for the alkali metals Li to Cs. (b) for the Period 3 elements Na to CI. The IB Data booklet gives the atomic and ionic radii of elements. State and explain the difference between (a) the atomic radius of nitrogen and oxygen (b) the atomic radius of nitrogen and phosphorus (c) the atomic and ionic radius of nitrogen

20 Chempocalypse Now! Chapter 08 Periodic Trends Page 20 Which is an essential feature of a ligand? A. a negative charge B. an odd number of electrons C. the presence of two or more atoms D. the presence of a non-bonding pair of electrons By reference to the structure and bonding in the compounds NaCI and SiCI 4 : (a) state and explain the differences in conductivity in the liquid state. (b) predict an approximate ph value for a solution formed by adding each compound separately to water. Elements with atomic number 21 to 30 are d-block elements. (a) Identify which of these elements are not considered to be typical transition elements. (b) Complex ions consist of a central metal ion surrounded by ligands. Define the term ligand. (c) Complete the table below to show the oxidation state of the transition element. Ion Oxidation State Cr 2 O 7 2 [CuCl 4 ] 2 [Fe(H 2 O) 6 ] 3+ (d) Identify two transition elements used as catalysts in industrial processes, stating the process in each case. (e) Apart from the formation of complex ions and apart from their use as catalysts, state two other properties of transition elements.

21 Chempocalypse Now! Chapter 08 Periodic Trends Page 21 (a) State two possible oxidation states for iron and explain these in terms of electron arrangements. (b) Explain why many compounds of d-block (transition) elements are colored. The color of transition metal complexes depends on several factors. (a) Use [Mn(H 2 O) 6 ] 2+ and [Fe(H 2 O) 6 ] 2+ as examples to outline why the color depends on the identity of the transition metal itself. (b) Outline why the color depends on the oxidation state of the transition metal. (c) Outline why the color depends on the identity of the ligand. Explain, in terms of their structure and bonding, why the element sulfur is a nonconductor of electricity and aluminum is a good conductor of electricity. Explain, in terms of its structure and bonding, why silicon dioxide, SiO 2, has a high melting point.

22 Chempocalypse Now! Chapter 08 Periodic Trends Page 22 Solve each of the following Paper 2 problems. Show any work in the space provided or on a separate piece of paper. 03M204

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