Presentation on theme: "The Halogens Group VII. Known as halogens – Derived from Greek, Salt maker – React with metals to form salts Astatine doesn’t really exist for a long."— Presentation transcript:
The Halogens 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 VII F Cl Br I At
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 VII F Cl Br I At
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 VII F Cl Br I At
Compounds Solubility – Chlorine and Bromine are fairly soluble in water – They react reversibly – Cl 2 +H 2 O 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. VII F Cl Br I At
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.
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.
Reactions of the Halogens Reactions with Metals
Reactions of the Halogens Reactions with phosphorus
Reactions of the Halogens Reactions with solutions of other halides
Reactions of the Halogens Reactions with water
Reactions of the Halogens Reactions with alkali
Reactions of the Halogens Reactions with reducing agents
Reactions of the Halogens Reactions with sodium thiosulphate