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The Halogens

The Halogens. Group VII. Group VII. Known as halogens Derived from Greek, Salt maker React with metals to form salts Astatine doesn’t really exist for a long enough time to explore its chemistry we predict its reactions by observing trends. At RTP. Fluorine Pale yellow gas Chlorine

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The Halogens

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  1. The Halogens Group VII

  2. Group VII • Known as halogens • Derived from Greek, Salt maker • React with metals to form salts • Astatine doesn’t really exist for a long enough time to explore its chemistry • we predict its reactions by observing trends

  3. At RTP • Fluorine • Pale yellow gas • Chlorine • Pale green gas • Bleaches damp litmus • Bromine • Brown Liquid (evaporates easily to a brown gas) • Does nasty things to skin! • Iodine • Dark grey / black crystals • Sublimes to a violet vapour on gentle heating

  4. Properties • Electron configuration • 5 p electrons. • Atomic Radius • Increases down the group • Ionic radius • Increases down the group • First Ionisation energy • Decreases down group • First Electron Affinity • Decreases down group • Electronegativity. • Decreases from F - I

  5. Compounds • Solubility • Chlorine and Bromine are fairly soluble in water • They react reversibly • Cl2 +H2O  HCl + HOCl • Aqueous solutions are called Chlorine or Bromine water • Chlorine water is (just about) pale green • Bromine water is orangey brown – red • Iodine is only slightly soluble in water • Halogens are much more soluble in hexane.

  6. Bonding in halogens • Ionic Bonding • All the Halogens form X- ions • With group I & II • Ionic bonding • With group III • Aluminium fluoride • Ionic • Aluminium chloride varies depending on whether it is anhydrous or not. • With d-block metals • Covelant when anhydrous • Ionic with water.

  7. Bonding in halogens • Covalent Bonding • Polar covalent bonds with almost all non metals • Fluorine is always in the -1 oxidation state • Chlorine is in the -1 oxidation state unless bonded with fluorine or oxygen • Halogens other than fluorine have empty d-orbitals so it is possible to promote electrons from the p-orbital into the energetically similar d-orbital • This allows more than one covalent bond to be formed. • This only happens when bonded to a small very electronegative atom such as oxygen.

  8. Reactions of the Halogens • Reactions with Metals

  9. Reactions of the Halogens • Reactions with phosphorus

  10. Reactions of the Halogens • Reactions with solutions of other halides

  11. Reactions of the Halogens • Reactions with water

  12. Reactions of the Halogens • Reactions with alkali

  13. Reactions of the Halogens • Reactions with reducing agents

  14. Reactions of the Halogens • Reactions with sodium thiosulphate

  15. Hydrogen Halides

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