GROUP VII The Halogens 2010 i
GROUP VII The Halogens A guide for iGCSE students 2010 KNOCKHARDY PUBLISHING SPECIFICATIONS GROUP VII INTRODUCTION This Powerpoint show is one of several produced to help students understand selected GCSE Chemistry topics. It is based on the requirements of the AQA specification but is suitable for other examination boards. Individual students may use the material at home for revision purposes and it can also prove useful for classroom teaching with an interactive white board. Additional Powerpoints, and the full range of AS and A2 Chemistry topics, are available from the KNOCKHARDY WEBSITE at... www.knockhardy.org.uk All diagrams and animations in this Powerpoint are original and created by Jonathan Hopton. Permission must be obtained for their use in any commercial work. GROUP VII CONTENTS • Introduction • Group trends • Group similarities • Reaction with metals • Displacement reactions • Summary • Quick quiz • Hydrogen chloride or hydrochloric acid? INTRODUCTION THE HALOGENS OCCUR IN GROUP VII OF THE PERIODIC TABLE 0 Group 1 2 3 4 5 6 7 F Cl Br I At INTRODUCTION THE HALOGENS OCCUR IN GROUP VII OF THE PERIODIC TABLE 0 Group 1 2 3 4 5 6 7 F Cl Br I At THEY ARE NON-METALS AND HAVE ELECTRONIC CONFIGURATIONS JUST ONE ELECTRON SHORT OF THE NEAREST NOBLE GAS GROUP PROPERTIES GENERAL • • • • • non-metals exist as separate diatomic molecules… eg Cl2 have seven electrons in their outer shells form negative ions with a 1- charge reaction with metals and halides GROUP PROPERTIES GENERAL • • • • • non-metals exist as separate diatomic molecules… eg Cl2 have seven electrons in their outer shells form negative ions with a 1- charge reaction with metals and halides TRENDS • • • • • appearance boiling point electronic configuration atomic size ionic size • reactivity GROUP TRENDS GROUP TRENDS APPEARANCE F2 Cl2 Br2 I2 Colour Yellow Green Red/brown Grey State (at RTP) GAS GAS LIQUID SOLID Vapour colour Yellow Green Red/brown Purple GROUP TRENDS APPEARANCE F2 Cl2 Br2 I2 Colour Yellow Green Red/brown Grey State (at RTP) GAS GAS LIQUID SOLID Vapour colour Yellow Green Red/brown Purple BOILING POINT Boiling point / °C F2 Cl2 Br2 I2 - 188 - 34 58 183 INCREASES down Group because more energy is required to separate the larger molecules. GROUP TRENDS ELECTRONIC CONFIGURATION F Cl Br I Atomic Number 9 17 35 53 Configuration 2,7 2,8,7 2,8,18,7 2,8,18,18,7 • electrons go into shells further from the nucleus GROUP TRENDS ATOMIC & IONIC RADIUS Atomic radius / nm NOT TO SCALE F Cl Br I 0.064 0.099 0.111 0.128 GROUP TRENDS ATOMIC & IONIC RADIUS Atomic radius / nm Ionic radius / nm F Cl Br I 0.064 0.099 0.111 0.128 F¯ Cl¯ Br¯ I¯ 0.136 0.181 0.195 0.216 ATOMIC RADIUS INCREASES down Group IONIC RADIUS INCREASES down Group • the greater the atomic number the more electrons there are these go into shells increasingly further from the nucleus • ions are larger than atoms - the added electron repels the others so radius gets larger GROUP SIMILARITIES GROUP SIMILARITIES ELECTRONIC CONFIGURATION F Cl Br I Atomic Number 9 17 35 53 Configuration 2,7 2,8,7 2,8,18,7 2,8,18,18,7 • all the atoms have seven electrons in their outer shell • ions are larger than atoms - the added electron repels the others so radius gets larger GROUP SIMILARITIES MOLECULAR FORMULA F Cl Br I Molecular formula F2 Cl2 Br2 I2 Bonding Covalent Covalent Covalent Covalent • all exist as diatomic molecules NOT TO SCALE GROUP SIMILARITIES ION FORMATION F Cl Br I Ion F¯ Cl¯ Br¯ I¯ Configuration 2,8 2,8,8 2,8,18,8 2,8,18,18,8 • all gain one electron to form a negative ion of charge 1• ions are larger than atoms • the smaller the atom the easier it forms an ion GROUP SIMILARITIES ION FORMATION F Cl Br I Ion F¯ Cl¯ Br¯ I¯ Configuration 2,8 2,8,8 2,8,18,8 2,8,18,18,8 • all gain one electron to form a negative ion of charge 1• ions are larger than atoms • the smaller the atom the easier it forms an ion REACTIVITY F Reactivity Cl Br I Increasingly reactive • reactivity decreases down the Group / increases up the Group REACTIONS OF HALOGENS 1. WITH METALS 2. WITH HALIDES REACTION OF HALOGENS WITH METALS REACTION OF HALOGENS WITH METALS HALOGENS REACT WITH METALS TO PRODUCE METAL HALIDES. REACTION OF HALOGENS WITH METALS HALOGENS REACT WITH METALS TO PRODUCE METAL HALIDES. THE EASE OF REACTION DECREASES DOWN THE GROUP F > Cl > Br > I REACTION OF HALOGENS WITH METALS HALOGENS REACT WITH METALS TO PRODUCE METAL HALIDES. THE EASE OF REACTION DECREASES DOWN THE GROUP F > Cl > Br > I THIS IS BECAUSE ‘THE LARGER THE HALOGEN ATOM, THE LESS EASILY IT ATTRACTS THE ELECTRON IT NEEDS TO FILL ITS OUTER SHELL’ REACTION OF HALOGENS WITH METALS HALOGENS REACT WITH METALS TO PRODUCE METAL HALIDES. THE EASE OF REACTION DECREASES DOWN THE GROUP F > Cl > Br > I THIS IS BECAUSE ‘THE LARGER THE HALOGEN ATOM, THE LESS EASILY IT ATTRACTS THE ELECTRON IT NEEDS TO FILL ITS OUTER SHELL’ THE HALIDES OF GROUP I ARE… WHITE IONIC SOLIDS VERY SOLUBLE IN WATER SODIUM CHLORIDE (NaCl) IS A TYPICAL GROUP I HALIDE REACTION WITH ALKALI METALS REACTION WITH ALKALI METALS - Equations SODIUM + CHLORINE SODIUM CHLORIDE REACTION WITH ALKALI METALS - Equations Na SODIUM + Cl2 NaCl CHLORINE SODIUM CHLORIDE REACTION WITH ALKALI METALS - Equations Na SODIUM + Cl2 NaCl CHLORINE SODIUM CHLORIDE The equation doesn’t balance - multiply the formulae until it does REACTION WITH ALKALI METALS - Equations Na + SODIUM 2Na + Cl2 NaCl CHLORINE SODIUM CHLORIDE Cl2 2NaCl Balanced equation SODIUM CHLORIDE FORMATION Na Cl SODIUM ATOM 2,8,1 CHLORINE ATOM 2,8,7 11 protons; 11 electrons 17 protons; 17 electrons SODIUM CHLORIDE FORMATION Na+ Cl SODIUM ION 2,8 CHLORIDE ION 2,8,8 11 protons; 10 electrons 17 protons; 18 electrons both species now have ‘full’ outer shells; ie they have the electronic configuration of a noble gas SODIUM CHLORIDE FORMATION Na+ Cl SODIUM ION 2,8 CHLORIDE ION 2,8,8 Na Na+ 2,8,1 2,8 + e¯ ELECTRON TRANSFERRED Cl 2,8,7 + e¯ Cl¯ 2,8,8 DISPLACEMENT REACTIONS OF HALOGENS DISPLACEMENT REACTIONS OF HALOGENS HALOGENS GET LESS REACTIVE AS THE GROUP IS DESCENDED DISPLACEMENT REACTIONS OF HALOGENS HALOGENS GET LESS REACTIVE AS THE GROUP IS DESCENDED THIS DECREASE IN REACTIVITY DOWN THE GROUP CAN BE DEMONSTRATED USING DISPLACEMENT REACTIONS... A DISPLACEMENT REACTION IS WHERE ONE SPECIES TAKES THE PLACE OF ANOTHER IN A COMPOUND. DISPLACEMENT REACTIONS OF HALOGENS HALOGENS GET LESS REACTIVE AS THE GROUP IS DESCENDED THIS DECREASE IN REACTIVITY DOWN THE GROUP CAN BE DEMONSTRATED USING DISPLACEMENT REACTIONS... A DISPLACEMENT REACTION IS WHERE ONE SPECIES TAKES THE PLACE OF ANOTHER IN A COMPOUND. THE REACTIONS ARE EXAMPLES OF REDOX REACTIONS DISPLACEMENT REACTIONS OF HALOGENS CHLORINE WATER Pale green BROMINE WATER Orange SODIUM CHLORIDE SOLUTION Colourless SODIUM BROMIDE SOLUTION Colourless SODIUM IODIDE SOLUTION Colourless A SOLUTION OF THE HALOGEN IS ADDED TO A SOLUTION OF A HALIDE HALIDES ARE SALTS FORMED BETWEEN ELEMENTS AND HALOGENS DISPLACEMENT REACTIONS OF HALOGENS BROMINE WATER Orange SODIUM BROMIDE SOLUTION Colourless Experiment 1 CHLORINE WATER Pale green SODIUM CHLORIDE SOLUTION Colourless NO VISIBLE REACTION SODIUM IODIDE SOLUTION Colourless DISPLACEMENT REACTIONS OF HALOGENS BROMINE WATER Orange SODIUM CHLORIDE SOLUTION Colourless SODIUM IODIDE SOLUTION Colourless Experiment 2 CHLORINE WATER Pale green SODIUM BROMIDE SOLUTION Colourless BROMINE produced DISPLACEMENT REACTIONS OF HALOGENS BROMINE WATER Orange SODIUM CHLORIDE SOLUTION Colourless SODIUM BROMIDE SOLUTION Colourless Experiment 3 CHLORINE WATER Pale green SODIUM IODIDE SOLUTION Colourless IODINE produced DISPLACEMENT REACTIONS OF HALOGENS CHLORINE WATER Pale green SODIUM BROMIDE SOLUTION Colourless Experiment 4 BROMINE WATER Orange SODIUM CHLORIDE SOLUTION Colourless NO VISIBLE REACTION SODIUM IODIDE SOLUTION Colourless DISPLACEMENT REACTIONS OF HALOGENS CHLORINE WATER Pale green SODIUM CHLORIDE SOLUTION Colourless SODIUM IODIDE SOLUTION Colourless Experiment 5 BROMINE WATER Orange SODIUM BROMIDE SOLUTION Colourless NO VISIBLE REACTION DISPLACEMENT REACTIONS OF HALOGENS CHLORINE WATER Pale green SODIUM CHLORIDE SOLUTION Colourless SODIUM BROMIDE SOLUTION Colourless Experiment 6 BROMINE WATER Orange SODIUM IODIDE SOLUTION Colourless IODINE produced DISPLACEMENT REACTIONS OF HALOGENS SUMMARY OF OBSERVATIONS SODIUM CHLORIDE 1 SODIUM IODIDE 2 3 Solution goes from colourless to orangeyellow BROMINE FORMED Solution goes from colourless to orangered IODINE FORMED 4 5 6 Solution goes from colourless to orangeyellow NO REACTION Solution goes from colourless to orangeyellow NO REACTION Solution stays colourless CHLORINE NO REACTION BROMINE SODIUM BROMIDE The colour change in Experiments 4 and 5 is due to dilution – there is no reaction Solution goes from colourless to red IODINE FORMED DISPLACEMENT REACTIONS OF HALOGENS EQUATIONS CHLORINE + SODIUM BROMIDE CHLORINE + SODIUM IODIDE BROMINE + SODIUM IODIDE DISPLACEMENT REACTIONS OF HALOGENS EQUATIONS CHLORINE + SODIUM BROMIDE BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM IODIDE IODINE + SODIUM CHLORIDE BROMINE + SODIUM IODIDE IODINE + SODIUM BROMIDE DISPLACEMENT REACTIONS OF HALOGENS EQUATIONS CHLORINE + SODIUM BROMIDE BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM IODIDE IODINE + SODIUM CHLORIDE BROMINE + SODIUM IODIDE IODINE + SODIUM BROMIDE Cl2(aq) + NaBr(aq) —> Br2(aq) + NaCl(aq) The equation doesn’t balance - multiply the formulae until it does DISPLACEMENT REACTIONS OF HALOGENS EQUATIONS CHLORINE + SODIUM BROMIDE BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM IODIDE IODINE + SODIUM CHLORIDE BROMINE + SODIUM IODIDE IODINE + SODIUM BROMIDE Cl2(aq) + NaBr(aq) Cl2(aq) + 2NaBr(aq) —> Br2(aq) + NaCl(aq) —> Br2(aq) + 2NaCl(aq) DISPLACEMENT REACTIONS OF HALOGENS EQUATIONS CHLORINE + SODIUM BROMIDE BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM IODIDE IODINE + SODIUM CHLORIDE BROMINE + SODIUM IODIDE IODINE + SODIUM BROMIDE Cl2(aq) + 2NaBr(aq) —> Br2(aq) + 2NaCl(aq) IONIC EQUATION Cl2(aq) + 2Br¯(aq) —> Br2(aq) + 2Cl¯(aq) DISPLACEMENT REACTIONS OF HALOGENS EQUATIONS CHLORINE + SODIUM BROMIDE BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM IODIDE IODINE + SODIUM CHLORIDE BROMINE + SODIUM IODIDE IODINE + SODIUM BROMIDE Cl2(aq) + 2NaI(aq) —> I2(aq) + 2NaCl(aq) IONIC EQUATION Cl2(aq) + 2I¯(aq) —> I2(aq) + 2Cl¯(aq) DISPLACEMENT REACTIONS OF HALOGENS EQUATIONS CHLORINE + SODIUM BROMIDE BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM IODIDE IODINE + SODIUM CHLORIDE BROMINE + SODIUM IODIDE IODINE + SODIUM BROMIDE Br2(aq) + 2NaI(aq) —> I2(aq) + 2NaBr(aq) IONIC EQUATION Br2(aq) + 2I¯(aq) —> I2(aq) + 2Br¯(aq) DISPLACEMENT REACTIONS OF HALOGENS SUMMARY CHLORINE + SODIUM BROMIDE BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM IODIDE IODINE + SODIUM CHLORIDE BROMINE + SODIUM IODIDE IODINE + SODIUM BROMIDE THIS SHOWS THAT A MORE REACTIVE HALOGEN WILL DISPLACE A LESS REACTIVE ONE FROM AN AQUEOUS SOLUTION OF ITS SALT DISPLACEMENT REACTIONS OF HALOGENS EQUATIONS CHLORINE + SODIUM BROMIDE BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM IODIDE IODINE + SODIUM CHLORIDE BROMINE + SODIUM IODIDE IODINE + SODIUM BROMIDE THIS SHOWS THAT A MORE REACTIVE HALOGEN WILL DISPLACE A LESS REACTIVE ONE FROM AN AQUEOUS SOLUTION OF ITS SALT HOWEVER, THIS REACTION DOES NOT TAKE PLACE BROMINE + SODIUM CHLORIDE CHLORINE + SODIUM BROMIDE (Bromine is below chlorine in the Group so is less reactive) DISPLACEMENT REACTIONS OF HALOGENS EXPLANATION 17+ CHLORINE ATOM 17 PROTONS 17 ELECTRONS 2,8,7 35+ BROMIDE ION 35 PROTONS 36 ELECTRONS 2,8,18,8 THE CHLORINE PRESS ATOMTHE PULLS SPACE AN ELECTRON BAR TO SEEOUT WHAT OF HAPPENS THE OUTER SHELL OF THE BROMIDE ION – THE CHLORINE ATOM BECOMES A CHLORIDE ION AND THE BROMIDE ION BECOMES A BROMINE ATOM. DISPLACEMENT REACTIONS OF HALOGENS EXPLANATION CHLORINE ATOM 17 PROTONS 17 ELECTRONS BROMIDE ION 35 PROTONS 36 ELECTRONS CHLORIDE ION 17 PROTONS 18 ELECTRONS BROMINE ATOM 35 PROTONS 35 ELECTRONS BECAUSE BROMINE ATOMS ARE LARGER THAN CHLORINE ATOMS, IT IS EASIER TO PULL ONE OF THEIR OUTER SHELL ELECTRONS OUT. CHLORINE NOW HAS THE OUTER SHELL ELECTRONIC CONFIGURATION OF A NOBLE GAS. DISPLACEMENT REACTIONS OF HALOGENS - REDOX DISPLACEMENT REACTIONS OF HALOGENS - REDOX A REDOX REACTION INVOLVES BOTH OXIDATION AND REDUCTION DISPLACEMENT REACTIONS OF HALOGENS - REDOX A REDOX REACTION INVOLVES BOTH OXIDATION AND REDUCTION REDUCTION IS THE… GAIN OF ELECTRONS OXIDATION IS THE… REMOVAL OF ELECTRONS DISPLACEMENT REACTIONS OF HALOGENS - REDOX A REDOX REACTION INVOLVES BOTH OXIDATION AND REDUCTION REDUCTION IS THE… GAIN OF ELECTRONS OXIDATION IS THE… REMOVAL OF ELECTRONS IN THE REACTION BETWEEN CHLORINE AND SODIUM BROMIDE, CHLORINE ATOMS PULL ELECTRONS OUT OF BROMIDE IONS. Cl2(aq) + 2Br¯(aq) ——> Br2(aq) + 2Cl¯(aq) DISPLACEMENT REACTIONS OF HALOGENS - REDOX A REDOX REACTION INVOLVES BOTH OXIDATION AND REDUCTION REDUCTION IS THE… GAIN OF ELECTRONS OXIDATION IS THE… REMOVAL OF ELECTRONS IN THE REACTION BETWEEN CHLORINE AND SODIUM BROMIDE, CHLORINE ATOMS PULL ELECTRONS OUT OF BROMIDE IONS. THE BROMIDE IONS ARE OXIDISED… CHLORINE IS THE OXIDISING AGENT ELECTRONS ARE REMOVED ELECTRONS REMOVED Cl2(aq) + 2Br¯(aq) ——> Br2(aq) + 2Cl¯(aq) OXIDISED DISPLACEMENT REACTIONS OF HALOGENS - REDOX A REDOX REACTION INVOLVES BOTH OXIDATION AND REDUCTION REDUCTION IS THE… GAIN OF ELECTRONS OXIDATION IS THE… REMOVAL OF ELECTRONS IN THE REACTION BETWEEN CHLORINE AND SODIUM BROMIDE, CHLORINE ATOMS PULL ELECTRONS OUT OF BROMIDE IONS. THE BROMIDE IONS ARE OXIDISED… THE CHLORINE ATOMS ARE REDUCED… ELECTRONS ARE REMOVED ELECTRONS ARE GAINED BROMIDE ION IS THE REDUCING AGENT Cl2(aq) + 2Br¯(aq) ——> Br2(aq) + 2Cl¯(aq) REDUCED GAIN OF ELECTRONS DISPLACEMENT REACTIONS OF HALOGENS - REDOX A REDOX REACTION INVOLVES BOTH OXIDATION AND REDUCTION REDUCTION IS THE… GAIN OF ELECTRONS OXIDATION IS THE… REMOVAL OF ELECTRONS IN THE REACTION BETWEEN CHLORINE AND SODIUM BROMIDE, CHLORINE ATOMS PULL ELECTRONS OUT OF BROMIDE IONS. THE BROMIDE IONS ARE OXIDISED… THE CHLORINE ATOMS ARE REDUCED… ELECTRONS ARE REMOVED ELECTRONS ARE GAINED ELECTRONS REMOVED Cl2(aq) + 2Br¯(aq) ——> Br2(aq) + 2Cl¯(aq) REDUCED OXIDISED GAIN OF ELECTRONS OXIDISING POWER OF HALOGENS HALOGENS GET LESS REACTIVE AS THE GROUP IS DESCENDED THIS IS DUE TO THEIR DECREASING OXIDISING ABILITY OXIDISING POWER OF HALOGENS HALOGENS GET LESS REACTIVE AS THE GROUP IS DESCENDED THIS IS DUE TO THEIR DECREASING OXIDISING ABILITY F Cl Br I Atomic Number 9 17 35 53 Configuration 2,7 2,8,7 2,8,18,7 2,8,18,18,7 Atomic radius / nm 0.064 0.099 0.111 0.128 ---- DECREASING OXIDISING POWER -----> OXIDISING POWER OF HALOGENS HALOGENS GET LESS REACTIVE AS THE GROUP IS DESCENDED THIS IS DUE TO THEIR DECREASING OXIDISING ABILITY F Cl Br I Atomic Number 9 17 35 53 Configuration 2,7 2,8,7 2,8,18,7 2,8,18,18,7 Atomic radius / nm 0.064 0.099 0.111 0.128 ---- DECREASING OXIDISING POWER -----> THE SMALLER THE HALOGEN, THE LESS SHIELDING THERE IS AND THE GREATER THE EFFECTIVE PULL OF THE NUCLEUS. OXIDISING POWER OF HALOGENS HALOGENS GET LESS REACTIVE AS THE GROUP IS DESCENDED THIS IS DUE TO THEIR DECREASING OXIDISING ABILITY F Cl Br I Atomic Number 9 17 35 53 Configuration 2,7 2,8,7 2,8,18,7 2,8,18,18,7 Atomic radius / nm 0.064 0.099 0.111 0.128 ---- DECREASING OXIDISING POWER -----> THE SMALLER THE HALOGEN, THE LESS SHIELDING THERE IS AND THE GREATER THE EFFECTIVE PULL OF THE NUCLEUS. THE GREATER THE PULL OF THE NUCLEUS, THE EASIER THE ATOM CAN PULL AN ELECTRON OUT OF ANOTHER SPECIES. OXIDISING POWER OF HALOGENS HALOGENS GET LESS REACTIVE AS THE GROUP IS DESCENDED THIS IS DUE TO THEIR DECREASING OXIDISING ABILITY F Cl Br I Atomic Number 9 17 35 53 Configuration 2,7 2,8,7 2,8,18,7 2,8,18,18,7 Atomic radius / nm 0.064 0.099 0.111 0.128 ---- DECREASING OXIDISING POWER -----> THE SMALLER THE HALOGEN, THE LESS SHIELDING THERE IS AND THE GREATER THE EFFECTIVE PULL OF THE NUCLEUS. THE GREATER THE PULL OF THE NUCLEUS, THE EASIER THE ATOM CAN PULL AN ELECTRON OUT OF ANOTHER SPECIES. CONSEQUENTLY, THE BIGGER THE ATOM, THE EASIER AN ELECTRON CAN BE REMOVED. GROUP VII - SUMMARY FLUORINE CHLORINE BROMINE IODINE SYMBOL F Cl Br I MOLECULAR FORMULA F2 Cl2 Br2 I2 APPEARANCE PALE YELLOW PALE GREEN RED-BROWN GREY-BLACK STATE (room temp) GAS GAS LIQUID SOLID COLOUR OF VAPOUR PALE YELLOW GREEN RED-BROWN PURPLE ELECTRONIC CONFIGURATION 2,7 2,8,7 2,8,18,7 2,8,18,18,7 INCREASES BOILING POINT ION (electronic config) F¯ Cl¯ Br¯ I¯ 2,8 2,8,8 2,8,18,8 2,8,18,18,8 REACTION WITH SODIUM PRODUCT OF REACTION WITH SODIUM LESS REACTIVE SODIUM FLUORIDE (NaF) SODIUM CHLORIDE (NaCl) SODIUM BROMIDE (NaBr) SODIUM IODIDE (NaI) QUICK QUIZ 1. ELEMENTS IN GROUP 7 ARE KNOWN AS THE ……… 2. WHAT ARE THE NAMES OF THE ELEMENTS 3. HOW DOES THE ATOMIC NUMBER CHANGE DOWN THE GROUP? 4. HOW DOES THE ELECTRONIC CONFIGURATION CHANGE? 5. HOW DOES THE ATOMIC SIZE (RADIUS) CHANGE? 6. HOW MANY ELECTRONS DO THEY HAVE IN THE OUTER LEVEL? 7. ARE THEY METALS OR NON-METALS? 8. WHAT HAPPENS TO THEIR COLOUR DOWN THE GROUP? 9. DO THEY GO AROUND IN PAIRS OR AS MONATOMIC GASES? 10. WHAT HAPPENS TO THEIR STATE AT ROOM TEMPERATURE? 11. WHAT TYPE OF COMPOUNDS DO THEY FORM WITH METALS? 12. HOW CAN EXPLAIN THEIR RELATIVE REACTIVITY IN TERMS OF THE ATOMIC STRUCTURE? QUICK QUIZ - ANSWERS 1. HALOGENS. 2. FLUORINE, CHLORINE, BROMINE, IODINE, ASTATINE. 3. ATOMIC NUMBER INCREASES DOWN THE GROUP. 4. GET MORE SHELLS DOWN THE GROUP. 5. ATOMIC SIZE INCREASES DOWN THE GROUP. 6. THEY ALL HAVE SEVEN ELECTRONS IN THE OUTER LEVEL. 7. THEY ARE NON-METALS. 8. COLOUR DARKENS DOWN THE GROUP. 9. ATOMS GO AROUND IN PAIRS OR AS DIATOMIC GASES. 10. GO FROM GAS TO SOLID DOWN THE GROUP. 11. THEY FORM IONIC COMPOUNDS WITH METALS. 12. THE LARGER THEY ARE THE LESS EASILY ELECTRONS ARE GAINED AND THE LESS REACTIVE THEY BECOME. HYDROGEN CHLORIDE OR HYDROCHLORIC ACID? HYDROGEN CHLORIDE OR HYDROCHLORIC ACID? Hydrogen chloride is a colourless covalent gas; it is a poor conductor of electricity because there are no free electrons or ions present. It has no action on dry litmus paper because there are no aqueous hydrogen ions present. HYDROGEN CHLORIDE OR HYDROCHLORIC ACID? Hydrogen chloride is a colourless covalent gas; it is a poor conductor of electricity because there are no free electrons or ions present. It has no action on dry litmus paper because there are no aqueous hydrogen ions present. HYDROGEN CHLORIDE OR HYDROCHLORIC ACID? Hydrogen chloride is a colourless covalent gas; it is a poor conductor of electricity because there are no free electrons or ions present. It has no action on dry litmus paper because there are no aqueous hydrogen ions present. In water, the hydrogen chloride molecules dissociate into ions. The solution now conducts electricity showing ions are present. For each hydrogen chloride molecule that dissociates (splits up) one hydrogen ion and one chloride ion are produced. The solution turns litmus paper red because of the H+(aq) ions. HYDROGEN CHLORIDE OR HYDROCHLORIC ACID? HYDROGEN CHLORIDE colourless gas covalent molecule HCl(g) poor no reaction HCl(g) HYDROCHLORIC ACID Appearance Bonding Formula Conductivity Dry blue litmus —> H+ (aq) colourless soln. aqueous ions HCl(aq) good goes red + Cl¯(aq) DOES HYDROGEN CHLORIDE ALWAYS DISSOCIATE? Hydrogen chloride dissociates in water because water is a polar solvent. However, when hydrogen chloride is placed in an organic solvent such as methylbenzene it does not dissociate and does not produce H+ ions. WATER A polar solvent Molecules dissociate The solution turns litmus paper red because of the H+(aq) ions. METHYLBENZENE A non-polar solvent NO dissociation The solution does not litmus paper red because there are NO H+(aq) ions. WHY DOES HYDROGEN CHLORIDE DISSOCIATE IN WATER? WATER IS A POLAR SOLVENT – it has one end which is slightly positive and another end which is slightly positive. negative end positive end WHY DOES HYDROGEN CHLORIDE DISSOCIATE IN WATER? WATER IS A POLAR SOLVENT – it has one end which is slightly positive and another end which is slightly positive. When a molecule of hydrogen chloride is put into water, the water molecules ‘encourage’ the covalent bond holding the hydrogen and chlorine atoms together to split, thus forming ions. HCl(g) —> H+ (aq) + Cl¯(aq) negative end positive end WHY DOES HYDROGEN CHLORIDE DISSOCIATE IN WATER? WATER IS A POLAR SOLVENT – it has one end which is slightly positive and another end which is slightly positive. When a molecule of hydrogen chloride is put into water, the water molecules ‘encourage’ the covalent bond holding the hydrogen and chlorine atoms together to split, thus forming ions. HCl(g) —> H+ (aq) + Cl¯(aq) The chloride ions are attracted to the slightly positive hydrogen end of water. The slightly negative oxygen end of water attracts the H+ ions. negative end positive end GROUP VII The Halogens THE END © 2011 KNOCKHARDY PUBLISHING & JONATHAN HOPTON
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