Periodicity

# Periodicity

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## Periodicity

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1. Periodicity Mr Field

2. Using this slide show • The slide show is here to provide structure to the lessons, but not to limit them….go off-piste when you need to! • Slide shows should be shared with students (preferable electronic to save paper) and they should add their own notes as they go along. • A good tip for students to improve understanding of the calculations is to get them to highlight numbers in the question and through the maths in different colours so they can see where numbers are coming from and going to. • The slide show is designed for my teaching style, and contains only the bare minimum of explanation, which I will elaborate on as I present it. Please adapt it to your teaching style, and add any notes that you feel necessary.

3. Menu: • Lesson 1 – The Periodic Table • Lesson 2 – Physical Properties • Lesson 3 – Chemical Trends • Lesson 4 – The Period 3 Oxides • Lesson 5 – HL – The Period 3 Oxides and Chlorides • Lesson 6 – HL – Transition Metals - Introduction • Lesson 7 – HL – Coloured Complexes and Catalysts • Lesson 8 – Test • Lesson 9 – Test Debrief

4. Lesson 1 The Periodic Table

5. Overview • Copy this onto an A4 page. You should add to it as a regular review throughout the unit.

6. Assessment • This unit will be assessed by: • A test at the end of the topic (100%)…around Lesson 8

7. We Are Here

8. Lesson 1: The Periodic Table • Objectives: • Reflect on prior knowledge of the periodic table • Understand the structure and purpose of the periodic table • Repeat the work of Mendeleev by constructing your own periodic table

9. Reflecting on the Periodic Table • What is the periodic table and what is supposed to show?

10. Wide Format Periodic TableShows true position of the f-block (lanthanides and actinides)

11. Janet Periodic TableElements arranged in order of orbital filling. Used frequently by physicists.

12. Benfey Periodic TableSpiral form shows the steady increase in atomic number.

13. Stowe Periodic TableEmphasises the symmetrical nature of the increase in quantum numbers.

14. Zymaczynski Periodic TableAnother way to show the symmetry in the underlying quantum numbers.

15. Giguere Periodic TableA 3D representation emphasising the s, p, d and f blocks

16. The Structure of the Periodic Table GROUPS PERIODS

17. Groups and Periods • Groups • Elements show similar chemical properties • Elements show similar trends in their chemical properties • Periods • As you move across periods, changes in the chemical and physical properties that are repeated in the next period • This is what ‘period’ and ‘periodic’ refers to

18. The periodic table and electron configuration • How does an element’s position in the PT relate to its electron configuration?

19. Being Mendeleev • The first widely accepted periodic table was produced by the Russian chemist Dmitri Mendeleev • It was a tremendous example of scientists as risk-takers as it was able to make a number of predictions thought unlikely at the time • Complete the exercise here in which you will use the information available to Mendeleev to construct your own periodic table

20. Homework – HL only! • In two groups, you need to work together to plan a 30 minute lesson on the objectives detailed below to be delivered in Lesson 5. • The lesson should include: • A presentation • Complete with equations, diagrams, explanations etc • An activity • A review • Allocations: • Group 1: 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. • Group 2: Describe the reactions of chlorine and the chlorides referred to above with water. State and explain the acidity of the resulting solutions • Oxides: Na2O, MgO, Al2O3, SiO2, P4O6 and P4O10, • SO2 and SO3, Cl2O and Cl2O7 • Chlorides: NaCl, MgCl2, Al2Cl6, SiCl4, PCl3 and PCl5, • and Cl2

21. SUPER IMPORTANT • (If you have one) bring a laptop with spreadsheet program to the next lesson. • If you don’t have Microsoft Excel, download OpenOffice for free from: • www.openoffice.org

22. Key Points • The periodic table arranges the elements according to: • Their chemical properties • Their electronic structure

23. Lesson 2 Physical Properties

24. Refresh • Nitrogen and silicon belong to different groups in the periodic table. • Distinguish in terms of electronic structure, between the terms group and period. • State the maximum number of orbitals in the n = 2 energy level.

25. We Are Here

26. Lesson 2: Physical Properties • Objectives: • Identify and explain the trends in the physical properties of the first 20 elements including: • Atomic radius • Ionic radius • First ionisation energy • Electronegativity • Melting point • Use Microsoft Excel to produce a spreadsheet to graph the above physical data

27. Atomic Radius • This is the ‘size’ of an atom • There is no simple measure as atoms do not have a well defined ‘edge’ • We use the: covalent radius • This is half the distance between the nuclei of two atoms in a covalent bond • This means we don’t have values for the noble gases as they do not form bonds • Values range from are measured in picometres ( 1 pm = 1x10-12 metres…a thousand-billionth of a metre) and range over: • 270 picometres Francium • 30 picometres for Hydrogen (helium would be smaller but does not form covalent bonds to be measured) • The main factors influencing atomic radius are: • Number of shells (the principal quantum number) • The charge in the nucleus

28. Ionic Radius • This is the ‘size’ of an ion and is measured in a similar way to atomic radius • It is measured in a picometres with values ranging over: • 272 pm for the Ge4- ion • 16 pm for the B3+ ion • The main factors influencing ionic radius are: • Number of shells (the principal quantum number)…don’t forget this can be affected by the type of ion formed • The charge in the nucleus

29. First ionisation energy • This is the energy required to remove one mole of electrons from one mole of gaseous atoms to form positive ions i.e.: A(g)  A+(g) + e- • Values range over: • 393 kJ mol-1 for Caesium • 1681 kJ mol-1 for Helium • Values are positive because this is an endothermic process • Values are influenced by: • Number of inner electron shells (and their shielding) • Charge on the nucleus • HL: At the finest level – repulsion between electrons in their orbitals

30. Electronegativity • This is a measure of the degree to which an element attracts the shared pair of electrons in a covalent bond • Again, this means there are no values for the noble gases • Values range over: • 4.0 for Fluorine • 0.7 for Francium • Values are influenced by: • Number of inner electron shells (and their shielding) • Charge on the nucleus • Values are unit-less as this is a relative measure

31. Melting Point • This is the temperature (in Kelvin…i.e. Celsius + 273) at which an element melts • Values range over: • 3935 K for Carbon • 1 K for Helium • Values are influenced by: • Nature of bonding: giant covalent, giant ionic, metallic • Strength of bonding • Strength of intermolecular forces

32. Trends in Physical Properties • You need to produce an Excel spreadsheet to help you analyse the physical data. • Use the blank here and follow the instructions on the instructions page • Once you have done this you need to use this to help you identify and explain the following trends: • Atomic and ionic radius, first ionisation energy, electronegativity and melting point • Down group I (alkali metals) • Down group VII (halogens) • Atomic and ionic radius, first ionisation energy, electronegativity • Across period 3 • The general trend in electronegativity over the whole PT

33. Key Points • Each of the following physical parameters follow trends and patterns in the PT • These patterns are generally explained by: • Charge in the nucleus • Number of electron shells • Electron shielding

34. Lesson 3 Chemical Properties

35. Refresh Which species has the largest radius? Do not use the data booklet…work it out! • Cl– • K • Na+ • K+

36. We Are Here

37. Lesson 3: Chemical Properties • Objectives: • Understand the following trends in reactivity: • Alkali metals with water • Alkali metals with halogens • Halogens with halide ions • Complete an experiment to investigate the above

38. Chemical Trends • Members of a group often have very similar reactivity. • You probably know that carbon will react with hydrogen to form methane, CH4 • You probably did not know that silicon will also react with hydrogen to form silane, SiH4 • Watch this demonstration to see some silane being made

39. Three reactions to know • The Group I (alkali) metals react with water as follows: • Metal + Water  Metal Hydroxide + Hydrogen • The Group I (alkali) metals react with halogens (Group VII) as follows: • Metal + Halogen  Metal Halide • Halogens can react with halide ions as follows (using the example of bromide and chlorine): • Bromide + Chlorine  Chloride + Bromine

40. Investigating chemical trends • In this experiment you will investigate trends in the reactions mentioned on the previous slide • Follow the instructions here

41. Key Points • Alkali metals become more reactive down the group: • Due to the outer shell electron becoming increasingly easy to remove • Halogens become less reactive down the group: • Due to the increased numbers of electron shells (and thus shielding) causing them to attract electrons less strongly

42. Lesson 4 Period 3 Oxides

43. Refresh Which properties of the alkali metals decrease going down group 1? • First ionization energy and reactivity • Melting point and atomic radius • Reactivity and electronegativity • First ionization energy and melting point

44. We Are Here

45. Lesson 4: Period 3 Oxides • Objectives: • Understand and explain the trend in acid-base behaviour of the period 3 oxides • Complete an experiment to demonstrate the amphoteric nature of aluminium oxide

46. The Period 3 Oxides • There is a gradual transition from basic to acidic character, reflecting a gradual transition from metallic to non-metallic nature • Note: you will only be tested on the elements marked with an asterisk, *

47. Amphoteric Aluminium • Complete the amphoteric aluminium experiment here. • This goes beyond the requirements of the syllabus but will help deepen your knowledge and understanding.

48. Homework • Research the role of acidic oxides in the formation of acid rain. • Include: • Sources of acidic oxides • Names and formulas and their reactions with water