Science Interactive LTD Science Interactive LTD. PO BOX 50764 LONDON NW6 9AT email: sales@science-interactive.co.uk web: www:science-interactive.co.uk Science Interactive LTD Copyright 2005 Science base multimedia CD-ROM for PC is a collection of 38 units or tools totalling over 1150 PowerPoint slides . Each unit covers a wide range of different delivery and learning styles, offering an exciting way to involve your pupils during lessons or revision sessions. All styles of teaching and learning are supported through use of high quality images , graphics , challenging exercises and questions . Units can be used in the classroom via an interactive whiteboard , data projector or used during individual study via a PC or school network . Unit 19: The Transitional Metals Unit 18: Metals and their Properties Unit 17: The Alkali Metals Unit 16: The Periodic Table and its Elements Unit 15: Genetic Engineering Unit 14: Evolution and Human Impact Unit 13: Inheritance and Selection Unit 12: Mitosis and Meiosis Unit 11: Flow of Energy and Elements through the Environment Unit 10: Water Transport in Plants Unit 9: Photosynthesis in Green Plants Unit 8: Drugs and Bad Body Maintenance Unit 7: Hormones and the Endocrine System Unit 6: Human Homeostasis Unit 5: Nervous System and the Senses Unit 4: The Respiratory System Unit 3: Healthy Body and Immunity Unit 2: The Circulatory System Unit 1: The Digestive System Unit 38: Cells, Tissue, Organs and Organs systems Unit 37: Natural Forces Unit 36: Sound and Hearing Unit 35: The Alkaline Earth Metals Unit 34: The Earth and Plate Tectonics Unit 33: Earth and Space Unit 32: Newton's Forces and the Effects of Forces Unit 31: Radioactivity Unit 30: Light and the Electromagnetic Spectrum Unit 29: Electricity Unit 28: Generating Electricity and its Domestic Use Unit 27: Energy Unit 26: Rates of Reaction Unit 25: The Noble Gases, their Properties and Uses Unit 24: The Halogens, their Uses and Compounds Unit 23: Ionic and Covalent Compounds Unit 22: Elements, Molecules and Compounds Unit 21: Rock Cycle Unit 20: Crude Oil and its Products

Unit 24 The Halogens, their Uses and Compounds Science Interactive LTD Copyright 2005

Unit 24

The Halogens, their Uses and Compounds

That group VII elements are called the halogens. The physical and chemical properties of the group VII elements, the halogens. That they have similar chemical and physical properties based on their electronic configuration. That the halogens can be involved in either ionic or covalent compounds. Their reactions and compounds with reactive metals. Their reactions and compounds with non metals. That their reactivity increases as you ascend the group. The uses of the halogens and their compounds. That the halogens and their compounds have antiseptic properties. Halogens, Halides, Physical, Chemical, Properties, Ionic, Covalent, Compounds, Metals, Non metals, Ions, Bonds, Reactions, Atoms, Molecules, Reactivity, Monatomic, Diatomic & Antiseptic. Unit 24: The Halogens, their Uses and Compounds web: www.science-interactive.co.uk email: sales@science-interactive.co.uk Science Interactive LTD PO BOX 50764 LONDON NW6 9AT Click mouse to begin Science Interactive LTD Copyright 2005 Understand: Keywords:

That group VII elements are called the halogens.

The physical and chemical properties of the group VII elements, the halogens.

That they have similar chemical and physical properties based on their electronic configuration.

That the halogens can be involved in either ionic or covalent compounds.

Their reactions and compounds with reactive metals.

Their reactions and compounds with non metals.

That their reactivity increases as you ascend the group.

The uses of the halogens and their compounds.

That the halogens and their compounds have antiseptic properties.

Physical properties of the halogens one Group VII of the periodic table contains a family of very r________ non-metals known as the halogens. This group contains fluorine, a pale yellow gas, chlorine a pale green gas, bromine a dark brown liquid and iodine a dark purple solid. They are not found in their pure state like gold, but are found tied up in c________ or ionic compounds. They have low melting and boiling points and do not conduct electricity at all. Give a use for the chloride and fluoride ion ? The halogens: Science Interactive LTD Copyright 2005 Word bank: reactive covalent The halogens have similar chemical properties because they all have seven electrons in their outer shell. Their colour darkens as you descend the group from fluorine a pale yellow gas to iodine a dark purple solid. Their melting and boiling points also rise as you descend the group. The halogens Notes Diagram Found in group VII of the periodic table, all the halogens have seven electrons in their outermost electron shell. They are therefore just one short of a full outer shell. This is what makes them reactive with other elements. Position of the halogens

Physical properties of the halogens two The group VII elements, the halogens are all reactive non-metals, able to form both ionic and covalent compounds with other elements. They have similar physical and chemical properties. They are all diatomic m_________. As you descend the group their colour deepens from pale yellow to dark purple. Their melting and b__________ points also increase with fluorine and chlorine being a gas, bromine a liquid and iodine a solid at room temperature. Give a definition of an ionic and covalent compound ? Physical properties of group VII halogens: Yellow Green Brown Purple 2,7 2,8,7 F 2 Cl 2 Br 2 I 2 2,8,18,7 2,8,18,18,7 Science Interactive LTD Copyright 2005 Word bank: molecules boiling 337 o C 59 o C -34 o C -188 o C Boiling point Solid Iodine Liquid Bromine Electron configuration Formula Colour Gas Gas State at room temperature Chlorine Fluorine Element Symbol

General antiseptic properties of the halogens The group VII elements, the halogens are well known for their antiseptic properties. Although they are very toxic to humans at high doses, small quantities of the halogens or their ions (F - Cl - Br - & I - ) have an antiseptic effect, destroying many m_______. Our drinking water is now chlorinated, making sure that we have clean w______ to drink. Our toothpaste contains fluoride to help reduce the amount of bacteria in your mouth. Before surgery, iodine water is applied to our skin to make sure that it is free from microbes. How else can we sterilise surfaces ? Antiseptic properties of group VII halogens: Science Interactive LTD Copyright 2005 Word bank: microbes water All the halogens are potentially harmful substances. Fluorine and chlorine in particular are highly toxic. It is highly dangerous to ingest or breathe halogen vapour or their solutions. They are used to kill bacteria therefore sterilising water for domestic supply or in swimming pools. Chlorine compounds are used in disinfectants like 'dettol' or 'TCP'. Iodine water is also used as a disinfectant prior to surgery or to sterilise dirty drinking water. Bromine Iodine Chlorine Fluorine

Properties and uses of fluorine Fluorine is a pale yellow diatomic gas. Two atoms of fluorine form a covalent molecule, where the atoms share a pair of electrons. Fluorine is the most reactive halogen. Fluorine is found in a wide range of chemicals including teflon a non stick inert coating for kitchen equipment like s_________. Small amounts of fluoride is found in toothpaste, to reduce bacteria in our mouths. Fluorine is also used in CFCs, a refrigerant now banned because of its effects on the o_______ layer. Find out about other uses of fluorine and its compounds ? Properties and uses of fluorine: Science Interactive LTD Copyright 2005 Word bank: saucepans ozone Fluoride Diatomic gas Fluorine is the most reactive and dangerous of the halogens. It was used during the first world war to make mustard gas which when inhaled would destroy your lungs within minutes. Fluorine forms an extremely stable non-stick compound called teflon. Developed by NASA scientists, it now coats millions of frying pans and artificial implants like hip replacement joints. Non-stick Refrigerants Fluorine is a pale yellow diatomic gas. Two atoms of fluorine covalently bond, sharing two electrons. The formula of fluorine is F 2 . Fluorine is the most reactive halogen. Fluorine

Properties and uses of chlorine Chlorine is a pale green diatomic gas. Two atoms of chlorine form a covalent molecule, where the atoms share a pair of electrons. Chlorine is the second most reactive halogen. Chlorine is found in a wide range of chemicals including bleach, a disinfectant used to clean surfaces, f______ and toilets. Small amounts of chloride is added to drinking water to kill any remaining b_________. Chlorine is also found in sodium chloride or table salt (excessive salt in the diet leads to high blood pressure and cardiovascular problems) Find out about other uses of chlorine and its compounds ? Properties and uses of chlorine: Science Interactive LTD Copyright 2005 Word bank: floors bacteria Bleach Diatomic gas Chlorine gas is very dangerous if inhaled but in small amounts it is extremely useful. Since we have chlorinated our drinking water, our life expectancy has risen dramatically over the decades. It is also added to swimming pools in higher concentrations to kill bacteria. Chlorine is also found in salt or sodium chloride (NaCl) Chlorination Salt Chlorine is a pale green diatomic gas. Two atoms of chlorine covalently bond sharing two electrons. The formula of chlorine is Cl 2 . Chlorine is the second most reactive halogen. Chlorine

Properties and uses of bromine Bromine is a dark brown diatomic liquid. Two atoms of bromine form a covalent molecule, where the atoms share a pair of e________. Bromine is the third most reactive halogen. Bromine is found in a wide range of chemicals including pesticides, which when sprayed on crops kills pests like locusts. Halon f______ extinguishers contain bromine which extinguishes small fires that cannot be put out using powder or water. Small amounts of bromine are added to plastics to prevent their decomposition by bacteria. This is useful for plastics that are used over long periods of time. Find out about other uses of bromine and its compounds ? Properties and uses of bromine: Science Interactive LTD Copyright 2005 Word bank: electrons fire Fire extinguishes Diatomic liquid Bromine is a very toxic brown liquid, but it does have several uses. Bromine toxicity is used to kill pests that destroy crops. Bromine is also used in fire extinguishers. It works by reacting with the oxygen, therefore preventing further combustion. Bromine is also added to plastics so that bacteria and moulds do not rot or decompose them. Pesticides Plastics Bromine is a brownish diatomic liquid. Two atoms of bromine covalently bond, sharing two electrons. The formula of bromine is Br 2 . Bromine is the third most reactive halogen Bromine

Properties and uses of iodine Iodine is a dark purple diatomic solid. Two atoms of iodine covalently bond sharing two electrons. Iodine is the l_______ reactive halogen. Iodine is found in high concentrations in certain seaweeds and in salt water. Iodine is used by the thyroid gland to make the h_________ thyroxin. Humans require small amounts of iodine in their diets. If iodine is lacking in the diet then goitre, a disease of the thyroid gland can develop. Iodine is also used to sterilise skin prior to surgical operations. Why don’t surgeons use bleach to sterilise the skin ? Properties and uses of iodine: Science Interactive LTD Copyright 2005 Word bank: least hormone Thyroid Diatomic solid Iodine is used by the human thyroid gland in order to produce thyroxine, an essential hormone. If your diet is poor in iodine, you may develop goitre which is a medical condition where your thyroid becomes enlarged. Iodine is also used to sterilise your skin prior to major surgery. It kills the bacteria on your skin. Explain why halogens, like iodine have an antiseptic effect ? Goitre Sterilisation Iodine is a deep purple diatomic solid. Two atoms of iodine covalently bond sharing two electrons. The formula of iodine is I 2 . Iodine is the least reactive halogen. Iodine

Reactions of the halogens The halogens can either gain electrons to form negative ions during the formation of ionic compounds or they can form a single covalent bond with other non metals during the formation of covalent compounds. They do this to become like n______ gases, having a full outer shell. The halogens can react with many metal and non metal elements forming a number of different ionic and covalent compounds, for example s_________ chloride (NaCl) and carbon tetra chlorine (CCl 4 ) Draw the electronic configuration of a single atom of fluorine and iodine ? Formation of ionic and covalent compounds: Sodium chloride Hydrochloric acid Sodium + Chlorine Hydrogen + Chlorine Science Interactive LTD Copyright 2005 Word bank: noble sodium During the formation of the covalent hydrochloric acid, both atoms form a single covalent bond. This sharing of electrons fills the outer shell of both hydrogen and chlorine atoms making them both stable. During the formation of sodium chloride (NaCl), a single electron from the outer shell of sodium is transferred to the outer shell of a single chlorine atom. Both ions (Na + & Cl - ) are now stable having the same electronic configuration as a noble gas. Notes Diagram Covalent compounds Ionic compounds

Ionic halide compounds All reactive metals found in groups I , II and III can form metal halide compounds by losing electrons to the halogens. This group of i______ metal halides includes sodium chloride. They are all soluble and mostly white crystalline solids. Draw a dot and cross diagram for NaI, MgBr 2 and FeBr 3 Ionic halide compounds: Lithium + Chlorine Lithium Chloride ( LiCl ) Magnesium Chloride ( MgCl 2 ) Aluminium Chloride ( AlCl 3 ) Group Atoms Ions of atoms Aluminium + Chlorine Magnesium + Chlorine x2 x3 Science Interactive LTD Copyright 2005 Word bank: ionic Others AlF 3 AlBr 3 AlI 3 Ratio Metal:Halogen 1:3 Others: MgF 2 MgBr 2 MgI 2 Ratio Metal:Halogen 1:2 Others: LiF LiBr LiI Ratio Metal:Halogen 1:1

Halogens also react with themselves and other non-metals to form covalent compounds by s__________ electrons with the halogens. Carbon tetra chlorine (CCl 4 ) is an important solvent used in dry cleaning. Draw a dot and cross diagram for C 2 H 4 Cl 2 . Covalent halide compounds: Covalent halide compounds Carbon + Chlorine Group Atoms Ions of atoms Chlorine + Chlorine Chlorine molecule ( Cl 2 ) Carbon tetra chlorine ( CCl 4 ) x2 Science Interactive LTD Copyright 2005 Word bank: sharing Ratio non metal:halogen 1:4 Others: F 2 Br 2 I 2 Ratio halogen:halogen 1:1

Displacement of halogens from their compounds The halogens become less reactive as you descend the group, for example reactions with other elements involving fluorine and chlorine occur without heating. Reactions with bromine only occur if heated and reactions involving iodine proceed slowly with strong heating. The reason why fluorine is the most r_________ halogen is because it’s the smallest atom and it is the best at capturing or gaining an electron from other e_________ during reactions. What's the rule for the group I metals ? Reactivity of the group VII halogens: Fluorine Chlorine Bromine Iodine Displaces Chlorine Bromine Iodine Displaces Bromine Iodine Displaces Iodine Displaces Nothing Displacement of halide ions from their solution Fluorine will displace chlorine, bromine and iodine ions from their solutions like KCl, KBr and KI, because it is the most reactive halogen. Science Interactive LTD Copyright 2005 Word bank: reactive element Reactivity of the halogens during reactions Reactivity

Electrolysis of brine (sodium chloride) Chlorine and its compounds are used in huge quantities around the World. Chlorine is extracted from sodium chloride using e____________. During electrolysis the sodium ion regains its single electron forming the metal: sodium. Conversely, the chloride ion loses its electron to form molecular chlorine gas which is then captured at the anode. Equation: Cathode: 2Na + + 2e - 2Na Anode: 2Cl - Cl 2 + 2e - Electrolysis of sodium chloride: Science Interactive LTD Copyright 2005 Word bank: electrolysis What happens during the electrolysis Concentrated sodium chloride or brine is added to the electrolysis cell. This is heated and allowed to become molten. The current is then switched on and electrolysis starts. Electrolysis of sodium chloride Chloride (Cl-) ions when molten are free to move. The chloride ions being negatively charged travel to the positive anode. Chloride ions (Cl - ) lose their electron and form diatomic chlorine (Cl 2. ) Chlorine is then used as a gas. Sodium (Na + ) ions when molten are free to move. The sodium ions being positively charged travel to the negative cathode and regain the electron lost. Molten sodium is formed at the cathode. Anode (+ve) Cathode (-ve)

1: Define the following terms: Halogens, Elements, Reactivity, Gases, Ionic and Covalent. 2: Look at the three pictures below. Complete the table. 3: Answer the following: a) From physical data, chlorine’s melting and boiling point is -101 o C and -35 o C. Between what temperatures would chlorine be a solid, liquid and gas. b) All the halogens are diatomic molecules. Explain this term. c) Name a compound in which a halogen can share an electron in a covalent bond. Do a dot & Cross diagram. d) Name a compound in which a halogen gain an electron to form an ion. Do a dot & cross diagram. e) State the type of bonding in the following compounds. Hydrogen fluoride, Lithium chloride, Tetra chloro-methane, Potassium bromide and Hydrochloric acid. f) Draw an atom of chlorine from the information given. Extension questions and homework 35.5 Cl 17 Science Interactive LTD Copyright 2005 Properties and uses Bromine Three Iodine Two Chlorine One Element Picture

4: Complete the following table. 5: Answer the following questions: a) The chemical reactivity of the halogens decreases as you go down the group. Explain why. b) The boiling and melting points of the halogens increases as you go down the group. Explain why. 6: Complete the following table: Write down the salts formed during the following reactions. Internet: Go to google.co.uk and find out the use of fluoride and chloride in drinking water. What form are they used and when were they first used and what do they aim to prevent. 7: Answer the following questions: a) How could you determine the pH of bromine liquid, chlorine gas and hydrogen chloride gas. b) What are silver halide films used for...clue you might have one if you have a suspected broken bone. c) If you electrolyse sodium chloride solution. (i) What ions would be attracted to the cathode (-ve) (ii) What ions would be attracted to the anode (+ve) (iii) Why is it impossible to form sodium when electrolysing a solution of sodium chloride...Explain your answer. Science Interactive LTD Copyright 2005 I Iodine Brown Bromine Gas Chlorine 7 Fluorine Symbol Colour State at room temperature Electrons in outer shell Halogen Sodium + Iodine Magnesium + Chlorine MgCl 2 Iron + Bromine Iron (III) Chloride Iron + Chlorine Formula Salt Reactants