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THE HALOGENS

THE HALOGENS. These are the Halogens or Group 7 Elements. H. He. Li. Be. B. C. N. O. F. Ne. F. Na. Mg. Al. Si. P. S. Cl. Ar. Cl. K. Ca. Sc. Ti. V. Cr. Mn. Fe. Co. Ni. Cu. Zn. Ga. Ge. As. Se. Br. Kr. Br. Rb. Sr. Y. Zr. Nb. Mo. Tc. Ru. Rh. Pd. Ag.

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THE HALOGENS

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  1. THE HALOGENS

  2. These are the Halogens or Group 7 Elements H He Li Be B C N O F Ne F Na Mg Al Si P S Cl Ar Cl K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Br Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe I Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn At Fr Ra Ac Rf Db Sg Bh Hs Mt ? ? ? Halogens and the Periodic Table

  3. All the Group 7 elements have 7 electrons in the outermost shell. F 2,7 Fluorine Cl Chlorine 2,8,7 Br Bromine I Iodine At Astatine Electronic Structure And so on

  4. All the Group 7 elements are molecules containing two atoms. (They are diatomic) Each atom is 1 electron short of a noble gas electron structure. By sharing electrons in a covalent bond full outer electron shells are achieved. F F F F Halogen molecules

  5. The group 7 elements get darker as you go down the group. Darker Bromine solution. Note the bromine vapour above the liquid F Cl Br I Patterns: colour What colour would you expect astatine to be?

  6. Melting Points and boiling points increase as the molecules get bigger. Patterns: physical state What is the physical state: solid, liquid or gas? gas gas liquid solid

  7. Reactivity increases up the group. F Cl Br I Increasing Reactivity At Patterns: reactivity How will Astatine react?

  8. Most halogen reactions involve gaining an electron. Reactivity and electron structures • The atoms get bigger as you go down the group. This reduces the attraction of the (+) nucleus for an additional (-) electron. • ‘Shielding’ by the inner electron shells also reduces the attraction from the nucleus. • As we go down the group the tendency to gain electrons decreases and so does the reactivity Reactivity decreases

  9. A more reactive halogen will displace a less reactive halide from its compounds in solution. very pale green no colour no colour red colour Displacement reactions Chlorine + sodium bromide  sodium chloride + bromine 2 NaCl(aq) + Br2(aq) Cl2(aq) + 2NaBr(aq) 

  10. The attraction of halogens for an extra electron gets greater going up the group: I <Br<Cl<F. If we mix a metal halide with a more reactive halogen, the electron will be transferred from the less to the more reactive halogen. Cl- e- F Na+ Na+ Cl F- Displacement theory

  11. The attraction of halogens for an extra electron means that they readily react with most metals. Chlorine reacts readily with iron on gentle heating despite iron’s low reactivity. Chlorine + iron  iron (III) chloride Reactions with metals 3Cl2(g) + 2Fe(s)  FeCl3 2

  12. Halogen atoms have 7 electrons in the outer shell. They seek to achieve a full shell (8 electrons). With metals they gain electrons forming ionic compounds. With non-metals they react by sharing electrons and forming covalent compounds. For example, hydrogen and chlorine form hydrogen chloride. Cl Cl H H Reactions with non-metals

  13. Fluorine, often via hydrogen fluoride, is used to manufacture many other products. Toothpaste, to prevent tooth decay Processing uranium nuclear fuel Fluoridation of water fluorine-containing polymers, e.g. Teflon Uses of Fluorine Fluorine and its compounds

  14. antiseptics and disinfectants pesticides and weed killer Chlorine and its compounds HCl Chlorinated carbon compounds, e.g. solvents and plastics (PVC) Bleach to kill bacteria and to make paper white Drinking water treatment Uses of Chlorine

  15. Uses of Bromine and Iodine Leaded petrol (being phased out) medicines photography agriculture antiseptic Animal feed supplements Bromine and its compounds Iodine and its compounds

  16. Link up the halogen with the uses. I F Cl Br Uses of Halogens

  17. Across: 2 Reactivity does this going up group 7 5 Added to animal feeds 7 Number of outer shell electrons in halogens 8 Used in the swimming pool 9 Used in photography Down: 1 Name for Group 7 Elements 3 Most reactive halogen 4 Type of compounds formed with non-metals 6 Type of compounds formed with metals 1 2 3 4 5 6 7 8 9

  18. How many electrons do the halogens have in their outer shell? 1 5 7 8

  19. How many atoms exist in a halogen molecule? 1 2 5 7

  20. What is the order of increasing reactivity of the halogens? F, Cl, I, Br F, Cl, Br, I I, Cl, Br, F I, Br, Cl, F

  21. Which of the pairs of reactants will NOT result in a displacement reaction? Iodine + sodium chloride Fluorine + sodium chloride Chlorine + sodium iodide Bromine + sodium iodide

  22. What halogen is used in non-stick cooking pans? F Cl Br I

  23. What halogen is used in animal feed? F Cl Br I

  24. Astatine comes below iodine in Group 7 What might its melting point be (in oC)? A. –225 B. +82 C. +150 D. +300

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