A group of non metal elements
The Halogens A group of non metal elements 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 Atomic radius Fluorine 0.072nm Chlorine 0.099nm Bromine 0.114nm
Iodine nm As atomic radius increases the strength of forces between molecules increase Trends in melting and boiling points Reflect on the information on the last two slides and come up with an explanation for the trends in melting and boiling points of the halogens Decreasing Reactivity
F Cl Cl Decreasing Reactivity Br Br I I At Sodium chlorine sodium chloride 2Na(s) Cl2 (g) NaCl(s) Electron arrangements of Halogens
Fluorine 2,7 Chlorine2,8,7 Bromine2,8,18,7 Iodine 2,8,18,8,7 What does each halogen need to fill its outer shell? What is happening to the attractive force of the nucleus for the outer shell as the Group is descended? Reactivity of the Halogens
Reflect upon the information and your answers to questions from the last two slides and explain the trend in reactivity Displacement reactions of halogens
A more reactive halogen will displace a less reactive halogen from a solution of its halide Potassium chloride KCl Potassium bromide KBr Potassium iodide KI Chlorine Cl2 reaction Bromine Br2 No reaction Iodine I2 Chlorine will displace both bromine and iodine
eg: Cl K+Br Br K+Cl- Bromine can only displace iodine. Br K+I I K+Br- Iodine cannot displace either chlorine or bromine. DISPLACEMENT REACIONS
Look carefully at what happens to the halogens and the halide ions in each of the reactions Look back at the explanation you produced for the trend in reactivity of the halogens Use these to explain why displacement reactions occur between halogens and halide ions Uses of Halogens Chlorine is used to purify water in swimming pools etc as it kills bacteria. Chlorine is also used as bleach. Iodine is used as an antiseptic on cuts and grazes.