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:
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.