A guide for iGCSE students KNOCKHARDY PUBLISHING GROUP VII The Halogens A guide for iGCSE students 2010 SPECIFICATIONS KNOCKHARDY PUBLISHING

GROUP VII www.knockhardy.org.uk 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?

THE HALOGENS OCCUR IN GROUP VII OF THE PERIODIC TABLE INTRODUCTION THE HALOGENS OCCUR IN GROUP VII OF THE PERIODIC TABLE Group 1 2 3 4 5 6 7 F Cl Br I At

THE HALOGENS OCCUR IN GROUP VII OF THE PERIODIC TABLE INTRODUCTION THE HALOGENS OCCUR IN GROUP VII OF THE PERIODIC TABLE 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 • exist as separate diatomic molecules… eg Cl2 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 • exist as separate diatomic molecules… eg Cl2 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 BOILING POINT 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 F2 Cl2 Br2 I2 Boiling point / °C - 188 - 34 58 183 INCREASES down Group because more energy is required to separate the larger molecules.

ELECTRONIC CONFIGURATION 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 F Cl Br I Atomic radius / nm 0.064 0.099 0.111 0.128 NOT TO SCALE

GROUP TRENDS ATOMIC & IONIC RADIUS ATOMIC RADIUS INCREASES down Group F Cl Br I Atomic radius / nm 0.064 0.099 0.111 0.128 F¯ Cl¯ Br¯ I¯ Ionic radius / nm 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

ELECTRONIC CONFIGURATION 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 • all exist as diatomic molecules 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 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

Increasingly reactive 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 Cl Br I Reactivity 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 + Cl2 NaCl SODIUM CHLORINE SODIUM CHLORIDE

REACTION WITH ALKALI METALS - Equations Na + Cl2 NaCl SODIUM CHLORINE SODIUM CHLORIDE The equation doesn’t balance - multiply the formulae until it does

REACTION WITH ALKALI METALS - Equations Na + Cl2 NaCl SODIUM CHLORINE SODIUM CHLORIDE 2Na + 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+ + e¯ 2,8,1 2,8 ELECTRON TRANSFERRED Cl + e¯ Cl¯ 2,8,7 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 SODIUM IODIDE SOLUTION Colourless Experiment 1 CHLORINE WATER Pale green SODIUM CHLORIDE SOLUTION Colourless NO VISIBLE REACTION

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 SODIUM IODIDE SOLUTION Colourless Experiment 4 BROMINE WATER Orange SODIUM CHLORIDE SOLUTION Colourless NO VISIBLE REACTION

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 SODIUM BROMIDE SODIUM IODIDE CHLORINE 1 Solution stays colourless NO REACTION Solution goes from colourless to orange-yellow BROMINE FORMED 2 3 Solution goes from colourless to orange-red IODINE FORMED BROMINE 4 Solution goes from colourless to orange-yellow NO REACTION Solution goes from colourless to orange-yellow NO REACTION 5 Solution goes from colourless to red IODINE FORMED 6 The colour change in Experiments 4 and 5 is due to dilution – there is no reaction

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) —> Br2(aq) + NaCl(aq) Cl2(aq) + 2NaBr(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+ 35+ CHLORINE ATOM 17 PROTONS 17 ELECTRONS 2,8,7 BROMIDE ION 35 PROTONS 36 ELECTRONS 2,8,18,8 THE CHLORINE ATOM PULLS AN ELECTRON OUT OF THE OUTER SHELL OF THE BROMIDE ION – THE CHLORINE ATOM BECOMES A CHLORIDE ION AND THE BROMIDE ION BECOMES A BROMINE ATOM. PRESS THE SPACE BAR TO SEE WHAT HAPPENS

DISPLACEMENT REACTIONS OF HALOGENS EXPLANATION CHLORIDE ION 17 PROTONS 18 ELECTRONS BROMINE ATOM 35 PROTONS 35 ELECTRONS CHLORINE ATOM 17 PROTONS 17 ELECTRONS BROMIDE ION 35 PROTONS 36 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… ELECTRONS ARE REMOVED CHLORINE IS THE OXIDISING AGENT 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… ELECTRONS ARE REMOVED THE CHLORINE ATOMS ARE REDUCED… 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… ELECTRONS ARE REMOVED THE CHLORINE ATOMS ARE REDUCED… 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 F Cl Br I F2 Cl2 Br2 I2 2,7 2,8,7 2,8,18,7 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 BOILING POINT INCREASES ION (electronic config) F¯ 2,8 Cl¯ 2,8,8 Br¯ 2,8,18,8 I¯ 2,8,18,18,8 REACTION WITH SODIUM LESS REACTIVE PRODUCT OF REACTION WITH SODIUM SODIUM FLUORIDE (NaF) SODIUM CHLORIDE (NaCl) SODIUM BROMIDE (NaBr) SODIUM IODIDE (NaI)

QUICK QUIZ ELEMENTS IN GROUP 7 ARE KNOWN AS THE ……… WHAT ARE THE NAMES OF THE ELEMENTS HOW DOES THE ATOMIC NUMBER CHANGE DOWN THE GROUP? HOW DOES THE ELECTRONIC CONFIGURATION CHANGE? HOW DOES THE ATOMIC SIZE (RADIUS) CHANGE? HOW MANY ELECTRONS DO THEY HAVE IN THE OUTER LEVEL? ARE THEY METALS OR NON-METALS? WHAT HAPPENS TO THEIR COLOUR DOWN THE GROUP? DO THEY GO AROUND IN PAIRS OR AS MONATOMIC GASES? WHAT HAPPENS TO THEIR STATE AT ROOM TEMPERATURE? WHAT TYPE OF COMPOUNDS DO THEY FORM WITH METALS? HOW CAN EXPLAIN THEIR RELATIVE REACTIVITY IN TERMS OF THE ATOMIC STRUCTURE?

QUICK QUIZ - ANSWERS HALOGENS. FLUORINE, CHLORINE, BROMINE, IODINE, ASTATINE. ATOMIC NUMBER INCREASES DOWN THE GROUP. GET MORE SHELLS DOWN THE GROUP. ATOMIC SIZE INCREASES DOWN THE GROUP. THEY ALL HAVE SEVEN ELECTRONS IN THE OUTER LEVEL. THEY ARE NON-METALS. COLOUR DARKENS DOWN THE GROUP. ATOMS GO AROUND IN PAIRS OR AS DIATOMIC GASES. GO FROM GAS TO SOLID DOWN THE GROUP. THEY FORM IONIC COMPOUNDS WITH METALS. 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 HYDROCHLORIC ACID colourless gas Appearance colourless soln. covalent molecule Bonding aqueous ions HCl(g) Formula HCl(aq) poor Conductivity good no reaction Dry blue litmus goes red HCl(g) —> H+ (aq) + 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. negative end positive end 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)

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 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.

© 2011 KNOCKHARDY PUBLISHING & JONATHAN HOPTON GROUP VII The Halogens THE END © 2011 KNOCKHARDY PUBLISHING & JONATHAN HOPTON