HOME PAGE * KS3 SCIENCES * GCSE BIOLOGY CHEMISTRY PHYSICS * ADVANCED LEVEL CHEMISTRY
GCSE Chemistry Notes: Physical and chemical properties of Group 7 Halogens Cl, Br, I
Group 7 HALOGEN elements of the Periodic Table
Group 7 of the Periodic Table – The physical and chemical properties of the halogens (non-metals)
Sub-index GCSE notes on the Group 7 Halogens
For advanced A Level student see Advanced A Level Chemistry Group 7/17 Halogen Notes BUT reading this page reminds you of what you theoretically leaned from GCSE/IGCSE/O Level courses on halogens! So this page can act as a primer for the study of the halogens chlorine, bromine iodine etc.
astatine * bleach * bromine * chemical characteristics * chlorine * data on the elements * displacement reaction electrolysis of NaCl * explaining reactivity trend * fluorine * hydrochloric acid * hydrogen halides * iodine naming halogen compounds * physical characteristics * PVC * reaction of sodium hydroxide and chlorine reaction with metals * reaction with hydrogen * silver halide photography * uses of chlorine uses of fluorine, bromine and iodine * uses of hydrogen * uses of sodium chloride * uses of sodium hydroxide Revision notes on the
physical and chemical properties of
the non-metal group 7 halogens, chemical reactions of
halogens, compounds of the halogens, explaining the reactivity trend of the
halogens, boiling/melting point trends, colour trend of halogens reactions
with halogen salts and metals, help when revising for AQA
GCSE chemistry, Edexcel GCSE chemistry, OCR GCSE gateway science chemistry,
OCR GCSE 21st century science chemistry GCSE 9-1 chemistry examinations.
Doc Brown's
chemistry revision notes: basic school chemistry science GCSE chemistry, IGCSE chemistry, O level
& ~US grades 8, 9 and 10 school science courses or equivalent for ~14-16 year old
science students for national examinations in chemistry Doc Brown's Chemistry KS4 science GCSE/IGCSE/O level Chemistry Revision Notes Revising Physical Properties, Chemical Reactions & Uses of the Group VII Halogen elements and their compounds particularly, salt (sodium chloride) and the many products derived from it in the chlor-alkali industry . The halogens – fluorine, chlorine, bromine, iodine, astatine, their physical properties, their chemical reactions and reactivity. The physical properties of the Group 7 halogens – fluorine, chlorine, bromine, iodine and astatine are described and detailed notes on the chemical displacement reactions of chlorine, bromine and iodine. The balanced molecular equations and ionic equations of the reactions of halogens, explaining the reactivity trend of the Group VII halogen elements, the uses of the halogens, uses of halide salts and halogen organochlorine compounds. These revision notes on the halogens should prove useful for the new AQA, Edexcel and OCR GCSE (9–1) chemistry science courses. 1. Where are the Group 7 Halogens in the Periodic Table?
The Group VII Halogens form the next to the last vertical column on the right of the Periodic Table, where you find most of the non–metallic elements. Therefore the Halogen is the next to the last element on the period from period 2 onwards. At the bottom of Group 7 is the radioactive halogen astatine (At) which is not shown. Note: Using 0 to denote the Group number of Noble Gases is very historic now since compounds of xenon known exhibiting a valency of 8. Because of the horizontal series of elements e.g. like the Sc to Zn block (10 elements), Groups 3 to 0 can also be numbered as Groups 13 to 18 to fit in with the actual number of vertical columns of elements. This can make things confusing, but there it is, classification is still in progress! THINKING AHEAD: From a working knowledge of the position of the Group 7 Halogen elements in the periodic table you should be able to predict the number of outer electrons of Group 7 Halogen elements, possible compound formulae of the Group 7 Halogens, reactions and symbol equations for Group 7 Halogens and the probable reactivity of a halogen in group 7 from its position in the periodic table and the physical properties of elements low down in the group like astatine. Group 7 elements are on the far right of the periodic table with 7 outer electrons (1 short of a noble gas structure) and so you would expect them to be very reactive non-metals and form singly charged negative ions. It is the similarity in electron structure (7 electrons in the outer shell) that makes the chemistry of group 7 halogen non-metals the same - group 7 chemistry! 2. Electronic structure and reactivity of Group 7 Halogens (non-metals) In the context of their position in the Periodic Table On reaction n on–metals readily form negative ions in compounds by gaining electrons e.g.chlorine ==> chloride: Cl2 + 2e– ===> 2Cl– (more simply Cl + e– ===> Cl– typical of Group 7 Halogens) oxygen ===> oxide: O2 + 4e– ==> 2O2– (more simply O + 2e– ===> O2– typical of Group 6 elements) These are typical electron changes when non-metallic elements in groups 6 and 7 react. The negative ions are formed directly from the non-metals like halogen atoms. Atoms usually react to give an electron arrangement with a full outer shell by losing, gaining or sharing electrons. Non-metallic elements on the on the far right-hand side of the periodic table, (apart from the very noble gases which already have a stable full outer shell), quite readily gain electrons into their outer shell, giving them a high reactivity in forming negative ions. The outer electrons of non-metals tend to be more strongly held than the outer electrons of metals and this is very much the case for group 7 halogens which are the elements the furthest on the right of the periodic table (bar the stable noble gases). Therefore, the group 7 halogens like fluorine, chlorine and bromine tend to be the most reactive non-metallic elements. For non-metals, it usually takes too much energy to remove to many electrons to give a stable positive ion electron arrangement, but its much easier for a non-metal, like those in group 6 or 7, to gain 2 or 1 electrons to give an electronically stable negative ion with a full outer shell of electrons like a noble gas. Group 6 and 7 elements also readily share the outer electrons of other non-metals to form covalent bonds e.g. H2O and H2S from group 6 (O, S) and for the group 7 halogens like chlorine, HCl and CCl4. Non-metals like group 7 halogens do NOT normally form positive ions. You would have to remove 7 electrons from a chlorine atom to make the ion Cl7+, and this requires far too much energy that any chemical reaction could deliver! The group 7 halogens require to gain or share the least electrons to form an ion or molecule in which the halogen atom has a very stable noble gas electron arrangement. This requires the least energy, so the group 7 halogens tend to be the most reactive non-metals on the right-hand side of the periodic table. These points and explanations are elaborated on by looking at the chemical reactions of halogens further down the page. 3. A general introduction to the Halogens (see also halogens data table below) The Halogens are typical non–metals and form the 7th Group in the Periodic Table (the vertical pink column above). 'Halogens' means 'salt formers' and the most common compound is sodium chloride which is found from natural evaporation as huge deposits of 'rock salt' or the even more abundant 'sea salt' in the seas and oceans. The halogens are next to the last element in any period from period 2 onwards.
The non-metallic halogens have seven outer electrons, in any period from period 2 onwards. This outer electron similarity of the halogens makes them behave in a chemically similar (e.g. similar formulae, similar reactions) and in a particularly reactive way and is a modern pre-requisite of a set of elements belonging to the same group. BUT their similarity in physical properties and chemical reactions fits in well with Mendeleev's original conception of a group classification.
Physical features and important physical trends down the Group with increasing atomic number (proton number)
4. Chemical features, similarities, physical property and reactivity trends Elements - non-metals on the on the far right-hand side of the periodic table, and apart from noble gases, quite readily gain an electron into their outer shell, giving them a high reactivity in forming negative ions or a covalent bond. The group 7 halogens have 7 outer electrons and only need to gain one electron to form a stable negative ion, or, share one electron to make a covalent bond, thus making them the most reactive non-metals of the periodic table.
5. Covalent and ionic bonding in Group 7 halogen compounds When halogens combine with other metals, ionic compounds are formed e.g. sodium chloride, magnesium chloride and aluminium fluoride, where the ionic bonding results from the attraction of the positive metal ion and the negative halide ion, formed by electron transfer. ONE
ONE
ONE
When the non–metallic halogens combine with other non–metals the result is a covalent bond in a covalent compound molecule, formed by electron sharing e.g.
You can use these trends to make predictions about the physical and chemical properties of group 7 halogen elements 6. The Reactivity Order and Halogen Displacement Reactions A more reactive halogen will displace a less reactive halogen from a solution of its compounds. Such experiments provide an experimental method for establishing the reactivity order down the group of halogens.
7. Oxidation–Reduction theory of halogen displacement reactions The halogen molecule is the electron acceptor (the oxidising agent) and is reduced by electron gain to form a halide ion The halide ion is the electron donor (the reducing agent) and is oxidised by electron loss to form a halogen molecule chlorine molecule + bromide ion ===> chloride ion + bromine molecule ionically the redox equations are written ...
8. Explaining the Reactivity Trend of the Group 7 Halogen Why are Group 7 Halogen non–metallic elements so reactive? Why do halogens get less reactive down the group with increase in atomic/proton number? How do we explain the reactivity trend of the group 7 halogens?
Br [2.8.18.7] + e– ==> Br– [2.8.18.8]– I [2.8.18.18.7] + e– ==> I– [2.8.18.18.8]–
9. Predicting the chemistry of astatine At - one of the most important ideas in using the periodic table (You won't find much on astatine in your textbooks!) Astatine, element 85, is highly radioactive element and dangerous to work with in the laboratory and any prior knowledge or expectation would allow safer working. However, by following the group 7 halogen element patterns and trends you can make good predictions as to how astatine will behave physically and chemically. You would expect astatine to consist of diatomic molecules (At2) have a higher melting point and boiling point than iodine. You expect it to form a singly charged negative ion, the astatide ion At-, by an astatine atom with 7 electrons in the outer shell, gaining one electron You would expect it to form ionic compounds with metals e.g. sodium astatide Na+At- or calcium astatide CaAt2 etc. For example, from the reactivity trend, you would expect astatine to be less reactive than iodine (above it) because the halogens get less reactive down the group i.e. F > Cl > Br > I > At Therefore you would expect e.g. chlorine, bromine or iodine to displace astatine from its salts, therefore, these three predicted halogen displacement reaction are, in word equations, in symbol equations and ionic redox equations as follows ...
You can also predict that astatine will form hydrogen astatide (HAt) that is very soluble in water to give a strong acid solution of pH 0-1, just like hydrochloric acid (HCl) etc. Note that you can predict the formulae of the astatine molecule and potassium astatide because astatine is in the same group as Cl, Br and I with the same number of outer electrons, same valency, therefore the formulae will fit into the same pattern e.g. the At2 diatomic element molecule, the ionic salt potassium astatide KI. If you have followed this lot, say to yourself, well done me and Mendeleev !!! Postscript: A few atoms of the 7th halogen element tennessine (Ts). They are highly unstable and radioactive, but if you could make sufficient of them, would Ts behave as a halogen and fit in with the group patterns? 10. QUALITATIVE TESTS FOR HALIDE IONS – the negative ions (anions) formed from the halogens To the suspected halide ion solution add a little dil. nitric acid and a few drops of silver nitrate solution. Depending on the halide ion you get a different coloured silver halide precipitate, summarised below.
Note: A simple chemical test for chlorine:
More details on these and other tests Revision notes on the physical and chemical properties of the non-metal group 7 halogens, chemical reactions of halogens, compounds of the halogens, explaining the reactivity trend of the halogens, boiling/melting point trends, colour trend of halogens reactions with halogen salts and metals, help when revising for AQA GCSE chemistry, Edexcel GCSE chemistry, OCR GCSE gateway science chemistry, OCR GCSE 21st century science chemistry GCSE 9-1 chemistry examinations. 11. Other Reactions of the Halogens Fluorine forms fluorides, chlorine forms chlorides and iodine forms iodides, and these compounds maybe ionic with metals or covalent with other non-metals for other important industrial reactions see Salt - sodium chloride - extraction - uses of halogens Reaction with hydrogen H2
REACTION of HALOGENS with METALS Most halogens readily react with metals, especially on heating, to form ionic compounds The charge on the halide ion formed is -1 Reaction of halogens with Group 1 Alkali Metals Li Na K etc.
All the alkali metals react with all of the halogens to produce white crystalline solids of the ionic compound.
Since the charge on the group 1 metal ions is +1, and the charge on halide ions is -1, its easy to predict the formula of any ionic compound formed between an alkali metal and a halogen i.e. a 1 : 1 ratio.
Pd = period,
Gp = group 1H Note
that H does not readily fit into any group
Group 1 Alkali Metals and Group 7 Halogens So, you can deduce the
following table of all the possible ionic compounds formed from
the Group 1 Alkali Metals and the non-metal Group 7 Halogen
elements.
Reaction of halogens with other metals
Revision notes on the physical and chemical properties of the non-metal group 7 halogens, chemical reactions of halogens, compounds of the halogens, explaining the reactivity trend of the halogens, boiling/melting point trends, colour trend of halogens reactions with halogen salts and metals, help when revising for AQA GCSE chemistry, Edexcel GCSE chemistry, OCR GCSE gateway science chemistry, OCR GCSE 21st century science chemistry GCSE 9-1 chemistry examinations. WHERE–WHAT NEXT? See also Salt - sodium chloride - extraction - uses of halogens
BUT reading this page reminds you of what you theoretically leaned from your GCSE/IGCSE/O Level courses on halogens! So this page can act as a primer for the study of the group 7/17 halogens chlorine, bromine iodine etc. OTHER RELATED WEBPAGES separate web pages
PLEASE NOTE that these LINKS are for Advanced Level (GCE A level) Students ONLY ADVANCED LEVEL INORGANIC CHEMISTRY Part 9 Group 7/17 Halogens sub–index: 9.1 Introduction, trends & Group 7/17 data * 9.2 Halogen displacement reaction and reactivity trend * 9.3 Reactions of halogens with other elements * 9.4 Reaction between halide salts and conc. sulfuric acid * 9.5 Tests for halogens and halide ions * 9.6 Extraction of halogens from natural sources * 9.7 Uses of halogens & compounds * 9.8 Oxidation & Reduction – more on redox reactions of halogens & halide ions * 9.9 Volumetric analysis – titrations involving halogens or halide ions * 9.10 Ozone, CFC's and halogen organic chemistry links * 9.11 Chemical bonding in halogen compounds * 9.12 Miscellaneous aspects of halogen chemistry aqa gcse 9-1 chemistry:: Know the elements in Group 7 halogens of the periodic table are known as the halogens and have similar reactions because they all have seven electrons in their outer shell. The halogens are non-metals and consist of molecules made of pairs of atoms. You should be able to describe the nature of the compounds formed when chlorine, bromine and iodine react with metals and non-metals. In Group 7 halogens, the further down the group an element is the higher its relative molecular mass, melting point and boiling point. In Group 7 halogens, the reactivity of the elements decreases going down the group. A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt - so you can predict the outcome of particular combinations of group 7 halogen elements and the salt of another halogen. You should be able to: explain how properties of the elements in Group 7 halogens depend on the outer shell of electrons of the atoms predict properties from given trends down the group. what is the group 7 halogens trend in melting points?, what is the group 7 halogens trend in boiling points? what is the reactivity trend for the group 7 halogens? discuss the chemical properties of group 7 halogens, what are the physical properties of the group 7 halogens, describe the displacement reactions of the group 7 halogens, explain the reactivity trend of the group 7 halogens, describe the reaction of group 7 halogens with hydrogen, keywords equations: astatine * bromine * chemical characteristics * chlorine * data on the elements * displacement reaction * explaining reactivity trend * fluorine * hydrogen halides * iodine * naming halogen compounds * physical characteristics * reaction with metals * Cl2(aq) + 2KBr(aq) ==> 2KCl(aq) + Br2(aq) * Cl2(aq) + 2KI(aq) ==> 2KCl(aq) + I2(aq) * Br2(aq) + 2KI(aq) ==> 2KBr(aq) + I2(aq) * Cl2(aq) + 2Br–(aq) ==> 2Cl–(aq) + Br2(aq) * Cl2(aq) + 2I–(aq) ==> 2Cl–(aq) + I2(aq) * Br2(aq) + 2I–(aq) ==> 2Br–(aq) + I2(aq) * Cl2(aq) + 2Br–(aq) ==> 2Cl–(aq) + Br2(aq) * Cl2(aq) + 2I–(aq) ==> 2Cl–(aq) + I2(aq) * Br2(aq) + 2I–(aq) ==> 2Br–(aq) + I2(aq) * H2(g) + Cl2(g) ==> 2HCl(g) * 2Na(s) + Cl2(g) ==> 2NaCl(s) * 2Al(s) + 3Cl2(g) ==> 2AlCl3(s) * 2Fe(s) + 3Cl2(g) ==> 2FeCl3(s) * 2NaCl (aq) + 2H2O (l) + elec. energy ==> 2NaOH (aq) + H2 (g) + Cl2 (g) * 2NaOH(aq) + Cl2(aq) ==> NaCl(aq) + NaClO(aq) + H2O(l) * H2(g) + Cl2(g) ==> 2HCl(g) * Cl2 + 2KBr ==> 2KCl + Br2 * Cl2 + 2KI ==> 2KCl + I2 * Br2 + 2KI ==> 2KBr + I2 * Cl2 + 2Br– ==> 2Cl– + Br2 * Cl2 + 2I– ==> 2Cl– + I2 * Br2 + 2I– ==> 2Br– + I2 * Cl2 + 2Br– ==> 2Cl– + Br2 * Cl2 + 2I– ==> 2Cl– + I2 * Br2 + 2I– ==> 2Br– + I2 * H2 + Cl2 ==> 2HCl * 2Na + Cl2 ==> 2NaCl * 2Al + 3Cl2 ==> 2AlCl3 * 2Fe + 3Cl2 ==> 2FeCl3 * 2NaCl + 2H2O + elec. energy ==> 2NaOH + H2 + Cl2 * 2NaOH + Cl2 ==> NaCl + NaClO + H2O * H2 + Cl2 ==> 2HCl * KS4 Science physical properties of halogens chemical reactions of chlorine bromine iodine GCSE chemistry guide notes on physical properties of halogens chemical reactions of chlorine bromine iodine for schools colleges academies science course tutors images pictures diagrams of apparatus for physical properties of halogens chlorine chemical reactions of chlorine bromine iodine investigations word balanced symbol equations of physical properties of halogens chemical reactions of chlorine bromine iodine science chemistry revision notes on physical properties of halogens bromine chemical reactions of chlorine bromine iodine revising the chemistry of physical properties of halogens chemical reactions of chlorine bromine iodine help in chemical understanding of physical properties of halogens chemical reactions of chlorine bromine iodine description of physical properties of halogens iodine chemical reactions of chlorine bromine iodine experiments for chemistry courses university courses in chemistry careers in chemistry jobs in the chemical industry laboratory assistant apprenticeships in chemistry technical internship in chemistry IGCSE chemistry physical properties of halogens chemical reactions of chlorine bromine iodine USA US grade 8 grade 9 grade10 physical properties of halogens chemical reactions of chlorine bromine iodine chemistry revision notes group 7 halogens AQA science GCSE chemistry group 7 halogens Edexcel science GCSE chemistry group 7 halogens OCR 21st century science GCSE chemistry group 7 halogens OCR Gateway science GCSE chemistry group 7 halogens WJEC gcse science chemistry group 7 halogens CCEA/CEA gcse science chemistry group 7 halogens notes for revising group 7 halogens IGCSE revision notes GCSE reactions chlorine bromine iodine KS4 Science revision notes on GCSE reactions chlorine bromine iodine GCSE guide notes on GCSE reactions chlorine bromine iodine for schools colleges academies science course tutors images pictures diagrams for GCSE reactions chlorine bromine iodine science revision notes on GCSE reactions chlorine bromine iodine for revising module topics notes to help on understanding of GCSE reactions chlorine bromine iodine university courses in science careers in science jobs in the industry laboratory assistant apprenticeships technical internships USA US grade 8 grade 9 grade10 AQA science GCSE notes on GCSE reactions chlorine bromine iodine Edexcel science notes on GCSE reactions chlorine bromine iodine for OCR 21st century science OCR GCSE Gateway science notes WJEC gcse science CCEA/CEA gcse science gcse chemistry revision free detailed notes on chemistry of halogens chlorine bromine iodine to help revise igcse chemistry igcse chemistry revision notes on chemistry of halogens chlorine bromine iodine O level chemistry revision free detailed notes on chemistry of halogens chlorine bromine iodine to help revise gcse chemistry free detailed notes on chemistry of halogens chlorine bromine iodine to help revise O level chemistry free online website to help revise chemistry of halogens chlorine bromine iodine for gcse chemistry free online website to help revise chemistry of halogens chlorine bromine iodine for igcse chemistry free online website to help revise O level chemistry of halogens chlorine bromine iodine chemistry how to succeed in questions on chemistry of halogens chlorine bromine iodine for gcse chemistry how to succeed at igcse chemistry how to succeed at O level chemistry a good website for free questions on chemistry of halogens chlorine bromine iodine to help to pass gcse chemistry questions on chemistry of halogens chlorine bromine iodine a good website for free help to pass igcse chemistry with revision notes on chemistry of halogens chlorine bromine iodine a good website for free help to pass O level chemistry GCSE (9–1, 9-5 & 5-1) science courses |
Doc Brown's Chemistry |
|
|