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UNIT 12 HALIGENS IGCSE PPT CHEMISTRY

PPT RELATED TO IGCSE SYLLABUS CHEMISTRY

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UNIT 12 HALIGENS IGCSE PPT CHEMISTRY

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  1. HALOGENS

  2. Learning Objectives Group 7 :HALOGENS -the colours and physical states of the elements -the properties of other halogens in this group -difference between hydrogen chloride gas and hydrochloric acid -explain, in terms of dissociation, why hydrogen chloride is acidic in water but not in methylbenzene -the relative reactivities of the elements in Group 7 -demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts -these displacement reactions as redox reactions.

  3. Section 2 Chemistry of the Elements • The Periodic Table • Group 1 Elements • Group 7 Elements • Oxygen and Oxides • Hydrogen and Water • Reactivity Series • Tests for ions and gases

  4. fluorine F chlorine Cl bromine Br iodine I astatine At The elements in group 7 of the periodic table, on the right, are called the halogens. Group 7 – the halogens-SALT FORMERS

  5. 1-WHY CALLED GROUP 7? The HALOGENS

  6. 2-CHARGE ON HALOGEN

  7. Group 7 elements – chlorine, bromine and iodine The HALOGENS All have seven electrons in their outer shell. To become stable they gain an electron and carry a charge of -1. eg. Br- I- Cl-

  8. 4-WHAT KINDA ELEMENTS THEY ARE? The HALOGENS Five non-metals

  9. 5-HOW THERE ATOMS EXISTS? The HALOGENS are diatomic – this means that they go around as paired atoms. Cl2 Br2

  10. Group 7 elements – chlorine, bromine and iodine The HALOGENS are diatomic – this means that they go around as paired atoms. Cl2 Brittle and crumbly when solid. Br2

  11. 6-WHAT IS PHYSICAL STATE OF HALOGEN All have coloured vapours. Chlorine and bromine are extremely pungent (causing a sharp or irritating sensation) Gas Gas Liquid Solid Solid

  12. is pale yellow is green-yellow is red-brown is blue-black. 7-What are the general properties of the halogens? All the halogens are: • non-metals and so do not conduct electricity • brittle and crumbly when solid • poisonous and smelly. They become darker in colour down the group:

  13. State at room temperature? • Chlorine is a yellow – green gas • Bromine is a red - brown liquid which easily evaporates to give an orange – brown vapour • Iodine is a grey – black solid which sublimes to give a violet vapour

  14. 7-What are the general properties of the halogens? Why are they called the ‘halogens’? Halogens are very reactive non metals. They are all toxic Or harmful because they are so reactive. They are also never found free in nature because of their reactivity – they are found as compounds with metals. These halogen-metal compounds are salts, which give halogens their name – ‘halo-gen’ means ‘salt-former’.

  15. Appearance What would you predict about the appearance of astatine?

  16. NOTES

  17. NOTES

  18. 7- MELTING AND BOILING POINTS TRENDS The HALOGENS Low melting and boiling points, increasing going down the group -Larger atomic size -Stronger intermolecular forces -More energy need to break it

  19. The melting and boiling points of the halogens increase down the group, as the molecules become bigger. Halogen Melting point (°C) Boiling point (°C) State Relative size -220 -118 gas -101 -34 gas -7 59 liquid 114 184 solid What is the state of each halogen at room temperature?

  20. 7-ARE THEY CONDUCTOR Because no delocalised electrons Poor conductors of heat and electricity, even when solid or liquid.

  21. 8-DESCRIBE REACTIVITY OF HALOGENS Going down the group, the halogens become less reactive. Difficult to attract electrons due to large size

  22. decrease in reactivity The iron wool experiment shows that the reactivity of halogens decreases as you go down the group. What is the reactivity of the halogens? Halogen Reaction with iron wool Iron wool burns and glows brightly. Iron wool glows but less brightly than with chlorine. Iron wool has a very slight glow. Astatine is the halogen that appears directly below iodine in the periodic table. SO IT WILL BE MORE LESS REACTIVE

  23. decrease in reactivity The reactivity of alkali metals decreases going down the group. What is the reason for this? REASONS • The atoms of each element get larger going down the group. F • This means that the outer shell gets further away from the nucleus and is shielded by more electron shells. Cl • The further the outer shell is from the positive attraction of the nucleus, the harder it is to attract another electron to complete the outer shell. Br • This is why the reactivity of the halogens decreases going down group 7.

  24. 9-CHEMICAL REACTIONS OF HALOGENS

  25. A- REACTIONS WITH HYDROGEN Halogens react with other non-metallic elements, such as hydrogen, to form molecular compounds: Eg. hydrogen + chlorine  hydrogen chloride H2(g) + Cl2(g)  2HCl(g)

  26. H Cl H Cl chlorine hydrogen hydrogen chloride For example, halogens react with hydrogen to create hydrogen halides. +  -Halogens share electrons with non-metals, and so react to form covalent compounds. -All hydrogen halides are gases. -They dissolve easily in water and become strong acids.

  27. What’s the difference between hydrogen chloride and hydrochloric acid (they both have the same chemical formula – HCl) Hydrogen chloride is gaseous at room temperature. Hydrochloric acid is an aqueous solution of hydrogen chloride – i.e. dissolved in water. HYDROGEN CHLORIDE HYDROCHLORIC ACID HCl (g) HCl (aq)

  28. Hydrogen chloride? Hydrogen chloride is a covalent compound. However, when dissolved in water it dissociates to the separate ions, H+ and CL-. The H+ ion gives it acidic properties.

  29. Hydrogen chloride? When dissolved in an organic solvent, such as methylbenzene, hydrogen chloride does not dissociate into separate ions, so does not show acidic properties.

  30. Reactions Of The Halogens And Hydrogen Than Water Summary: Halogens + Hydrogen  hydrogen halides HF, HCl, HBr, HI All four are gases and very soluble in water

  31. Reactions of the halogens WITH METALS Halogens react with metals to produce ionic salts The halogen atom gains one electron to form the halide ion which carries a charge of -1 eg. Lithium + chlorine  lithium chloride 2Li(s) + Cl2(g)  2LiCl(s)

  32. -The reactivity of halogens means that they readily react with most metals. How do the halogens react with metals? -This means that halogens and metals react to form ionic compounds. -These are metal halides, which are a type of salt. nickel (II) chloride copper (II) chloride

  33. halogen + iron  iron (III) halide iron (III)chloride iron (III)bromide + + bromine chlorine iron iron   + + 3Cl2(g) 3Br2(g) 2Fe(s) 2Fe(s)   2FeCl3(s) 2FeBr3(s) When a halogen reacts with iron it forms an iron halide: Equations of halogens and iron The word and chemical equationsfor the reaction between chlorine and iron are: What would the equation be for the reaction that forms iron (III) bromide?

  34. Reactions of the halogens WITH METALS=SALTS

  35. Reactions of the halogens And Metals=salts Summary: All are SOLIDS and very soluble in water Halogens + Aluminium  Aluminium trihalides AlF3, AlCl3, AlBr3, AlI3 All four are white solids

  36. DISPLACEMENT REACTIONS Describe experiments to demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts

  37. Describe experiments to demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts “In a displacement reaction a more reactive element will displace a less reactive element from a compound.” ?

  38. Halogen displacement reactions Remember that the reactivity of the halogens decreases as we go down the group, so Fluorine is the most reactive halogen, and Astatine is the least reactive – can you explain this trend in terms of the number of electron shells? (hint – think back to the Alkali metals)

  39. Halogen displacement reactions A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt. e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2

  40. Halogen displacement reactions A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt. e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 Cl2 KI solution Displaced iodine

  41. Halogen displacement reactions A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt. e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 Cl2 KI solution Displaced iodine

  42. sodiumchloride sodiumfluoride + + fluorine  chlorine + + F2(aq) 2NaCl(aq)  2NaF(aq) Cl2(aq) If a halogen is added to a solution of a compound containing a less reactive halogen, it will react with the compound and form a new one. Displacement of halogens This is called displacement. A more reactive halogen will alwaysdisplace a less reactive halide from its compounds in solution.

  43. salt (aq) potassiumchloride potassiumbromide potassiumiodide halogen chlorine bromine iodine The reactions between solutions of halogens and metal halides (salts) can be summarised in a table: Displacement reactions: summary 2KCl + Br2 2KCl + I2 no reaction 2KBr + I2 no reaction no reaction

  44. Understand these displacement reactions as redox reactions “A redox reaction is where both oxidation and reduction occur.” ?

  45. Hydrogen chloride? The loss of electrons from an atom is known as oxidation. The gain of electrons is known as reduction.

  46. Hydrogen chloride? Remember OILRIG Oxidation Is Loss = OIL Reduction Is Gain = RIG

  47. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl-

  48. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- iodine loses 2e- (2I-  I2)

  49. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- iodine loses 2e- (2I-  I2)

  50. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- iodine loses 2e- (2I-  I2) iodine has been oxidised

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