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METALS AND THEIR PROPERTIES, METALS, , NON-METALS, , About eighty per cent of the known, ments are metals. These are the. elements, possessing the characteristic properties such, , Non-metals are the elements that do not, conduct heat and electricity and are neither, , as lustre (shine), malleability, ductility,, , malleable nor ductile. They are brittle. Non-, , high densities, etc. In ancient time, people, , are not lustrous (not shiny), they have, metals, dull appearance. Non-metals are generally, , knew only eight metals-gold, silver, copper,, , soft and not strong. They are light substances, , electrical conductivity, thermal conductivity,, iron. tin, lead, mercury (quick-silver) and antimony. By the end of the eighteenth century,, chemists came to know about twenty metals., In 1869, when Mendeleev proposed his periodic table, he arranged about fifty. metallic, elements in the table. At present more than, eighty metalic elements are known to us., , During chemical reactions, metals can, , and non-sonorous (which do not make ringing, sound when struck). Some of the examples of, non-metals are : Carbon, Sulphur, Phos-, , phorus, Silicon, Hydrogen, Oxygen, Nitrogen,, , Chlorine, Bromine, lodine, Helium, Neon and, , Argon. The two allotropic forms of carbon, element, diamond and graphite, are also nonmetals., , form positive ions by losing electrons. Based, on this observation, we can write another, , non-metals, gaining electrons., , During chemical reactions,, , definition of metals as follows: Metals are the., , can form negative ions by, , elements, (except hydrogen), which form positive, electrons, , Based on this observation, we can write, , ions by, , (or, , losing, , donating, , electrons). For example, aluminium (AI) is a, metal which foras positively charged aluminium ions (Al° *) by losing electrons., Al, Al*+3e, In fact, metals are known as electroposi, tive elements because they can form positive, , ions bylosing electrons., , another definition of non-metals as follows, Non-metals are the elements which form negative ions by gaining electrons (or accepting, , electrons.) For example, oxygen (0) is a non-, , metal which forms negatively charged oxide, , ions (0)by gainingelectrons., 02, 0+2e, , Distinetion between Metals and Non-metals, Non-metals, , Metals, , Properties, Physical Properties, 1., , State, , Metals are solids at ordinary Non-metals exist in all the three, temperature. Exception Mercury 1s states, that is, solid, liquid and gas., a liquid., , 2., , 3., 4., , Lustre, , They possess lustre or shine., , They possess no lustre., , Malleability and, , Metals are generally malleable and Non-metals are neither malleable, , Ductility, , ductile., , nor ductile., , Hardness, , Metals are generally hard., , Non-metals possess varying hard-, , Exception: lodine and graphite., , ness., , Alkali metals are exceptions., , Diamond is an exception. It is the, hardest substance known to occur in, , nature., , 5. Density, , hey have high densities., , They generally possess low densities.

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Metals, , Non-metals, , Metals are good conductors of heat, , Non-metals are poor conductors at, heat and electricity. The only excen, , Properties, 6. Conductivity, , and electricity., , tion is, , graphite which is a good con-, , ductor of electricity., 7., , Melting and boil-, , They usually have high melting and, , ing points, , boiling points., , Their melting and boiling points are, , usually low. The only exceptions are, boron, carbon and silicon., , Chemical Properties, 1, , with, , Action, mineral acids, , Metals generally react with dilute Non-metals do not displace hydrogen, on reaction with dilute, mineral acids to liberate H2 gas., minerals, , acids, , 2. Nature of oxides, , They form basic oxides. For example, | Non-metals form acidic or neutral, Na20, MgO, etc. These oxides are | oxides. For example, S02, COz, P20s, are acidic whereas Co,, ionic in nature., N20, ete, are neutral. These oxides are, covalent in nature., , 3., , Combination with, , Metals generally do not combine with | Non-metals combine with hydrogen, , hydrogen. However, Li, Na, Ca, etc. to form stable hydrides. For example,, , hydrogen, , form unstable, , hydrides. For ex- HCl, HS, CH4, NH3, PH3, ete. These, , ample, LiH, NaH, CaH2, etc. These hydrides, hydrides are ionic in character., 4., , Combination with, halogens, , 5., , Electrochemical, , behaviour, , They combine with halogens to, form well dilute and stable crystal-, , are, , covalent in nature., , Non-metals form halides which are, unstable and, undergo hydrolysis, , line solids. For example, NaCl, KBr,, , readily. For example,. PCls, PCl3,, , etc., , etc., , Metals are electropositive in charac- Non-metals are electronegative in ,, ter. They form cations in solution and character. They form anions in soluare deposited on the cathode when tion and are liberated at the anode, electricity is passed through their when their salt solutions are sub-, , solutions., , jected to electrolysis. Hydrogen is an, exception. It usually forms positive, ions and is liberated at cathode., , CHEMICAL PROPERTIES, , reactions of various metals with oxygen,, , OF METALS, , water and acids, as well as displacement reac, , The Reactivity Series of Metals (or Activity, , tions, the metals have been arranged in a, , Series of Metals), Some metals are chemically very reac-, , tive whereas others are less reactive or unreactive. For example, potassium and sodium, react very, very rapidly with cold water, so, they are very reactive metals. Zinc and iron, react only with steam, so they are less reactive, matals. On the other hand, Copper and silver, do not react even with steam, so they are quite, , unreactive metals. On the basis of vigour of, , group or series according to their chemical, reactivity: The arrangement of metals in a, , vertical column in the order, , of decreasing, , reactivities is called reactivity series ofmetals, (or activity series of metals). In reactiviy, the, series, the most reactive metal is placed at, , top whereas the least reactive metal is placea, at the bottom. The reactivity series of the, , common metals is given below:

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NEALOGIEIN, , Reactivity Series (or Activity Series) of Metals, Na, , Calcium, , Ca, , These metals are, , Magnesium, , Mg, , more reactive, , Aluminium, Zinc, Iron, , Al, , than hydrogen, , Zn, Fe, , Tin, Lead, , Sn, Pb, , reactivity, , Hydrogen, Copper, , H, Cu, , These metals are, less reactive than, , Mercury, , Hg, , Silver, , hydrogen, , Gold, , Ag, Au, , the metals react with, oxides, , oxygen, , Metal+ Oxygen, , to, , form, , Potassium, , their, , 2Na20, , 4Na+ O2, , Sodium oxide, , Both these metals are so reactive that, of, they react violently. As a result, inthe reaction, they catch fire., , hear evolved, , (b) Magnesium occupies a lower position, , in the activity series. It reacts with oxygen, to form magupon heating and burns brightly, , nesium oxide., heat, , 2Mg, , +, , O2-, , 2MgO, Magnesium oxide, , It, (c)Iron is comparatively less, not burn. The, reacts with oxgen but does, FeO. Fe203 (Lron l1,, produet is a mixture of ferroso-ferric oxide., colled, or, reactive., , oxides), , Fe3O4, , brown in colour., heat, , 3Fe+, , 202, , Feg04, , or, , Ferroso-ferric oxide, , (d) Copper metal, , Metal oxide, , to form, Oxygen at room temperature, respective oxides., , (Leastreactive metal), , metal, , The order of the reactivity of the metals, towards air or oxygen is linked with their, positions in the activity series. This is illustrated with a few examples., and sodium react with, , (a), , Decreasing, chemical, , Reaction of metals uwith oxygen: Most of, , It is, , (Most reaetive metal), , Potassium, Sodium, , FeO.Fe2Os, Iron (II, III) oxides, , is, , less reactive, , even, , than iron. It reacts with oxygen on prolonged, to form a black, Oxide or cupric oxide., , heating, , mass, , of copper (I), , heat, , 2Cu+O2, , 2CuO, , Copper (1I) oxide or cupric oxide, (e) Silver and gold do not react with, oxygen even at very high temperature. This is, quite evident from their positions in the a c, tivity series., , Reaction of metals with water : Anumber, , of metals react with water to form a hydroxide, , or an oxide alongwith the evolution of, hydrogen gas. However, reactivity of different, metals is different. Some metals react with, water at room temperature, some of them, react on heating, some others react with, steam only whereas some do not react even, with steam.A few examples are given below:, , (i) Sodium and potassium react evena, with cold water so violently that hydrogen, evolved catches fire., , 2Na(s)+2H20U), Sodium, , Water, , 2NaOH(aq) + Ha(g), Sodium hydroxide Hydrogen, , K(s) +2H20(0)> 2KOH(«q) + Hog), , Potassium, , Water, , Potassium hydroxide, , Hydrogen, , (ii) Caleium also reacts with water at, room temperature forming calcium hydroxide, but the reaction is less violent.

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Mg(s) +2HCl(aq), , Room, , Ca(s)+2Hg0), , Ca(OH)z(aq) + Hak), , Water temp. Caleium hydroxide Hydrogon, , Calcium, , Further, the bubbles of hydrogen gas, , produced stick to the surface of calcium, , and, , MgCl2(aq) + Ho, Magnesium, , Magnesium Hydrochloric, , Hydrogen, , chloride, , acid, , (iv) Aluminium reacts with diluto, hydrochloric acíd slowly in the beginningh, cause the surface of aliminium is alreadu, , hence it starts floating., (ii) Magnesium does not react with cold, , covered with a protective layer of aluminium, , water. It reacts only with hot water forming, , oxide. However, after this layer gets dissolved, , magnesium hydroxide and hydrogen., , in the acid, the reaction becomes fast, as now, , Mg's)+2H200) -, , Mg(OH)2, , Magnesium (Hot water), , +, , H2, , Magnesium Hydrogen, hydroxide, , Civ) Aluminium, zinc and iron neither, react with cold water nor with hot water. They, , react only with steam to form metal oxide and, , hydrogen., , 2Al(s) +3H20(g), , Aluminium, , Al20s(s) + 3H2g), Aluminium, , Steam, , oxide, , Zn(s) +H20g)-, , Hydrogen, , ZnO(s)+ Hag), , Zincoxide Hydrogen, Steam, 3Fe(s)+4H20g)- » FegO4(s) + 4H2(g), Iron, Steam, Iron oxide, Hydrogen, Zinc, , (v) Lead, copper, silver and gold do not, react even with steam., , attack takes place on fresh aluminium sur-, , face., 2Al(s) + 6HCl(aq)- 2AICl3(aq) + 3H2lg), Aluminium, , acid, , giving out hydrogen gas., , Zn(s). + 2HCl(aq), Zinc, , Reaction of metals with dilute acids:, (i) Sodium and potassium react very, violently with dilute hydrochloric acid form, , Fe(s)+2HCl(ag), Irron, , acid, , Thus, the order of reactivity of metals, , towards dilute hydrochloric acid or dilute sulphuric acid, is in the order:, K> Na> Ca> Mg >Al> Zn >Fe>, Cu> Hg> Ag, , 2KClaq) + Ha(g), Potassium Hydrogen, , Reaction of metals uwith chlorine: Metals, react with chlorine to form metal chlorides., chloride, olReactive metals like sodium, potassium, ca, 2NaClaq) + H2(g), Sodium, , Hydrogen, , chloride, , (ii) Calcium also reacts vigorously, , though less than sodium and potassium, Ca(s)++2HCl(aq), , Calcium, , Hydrochloric, acid, , FeCla(aq) +Hag), , react with dilute hydrochloric acid or sulphuric acid as already mentioned., , hydrogen gas., 2Na(s)+ 2HCl(aq), Sodium'Hydrochloric, , Hydrogen, , Iron (EI) Hydrogen, chloride, acid, (vii) Copper, mercury and silver do not, , ing their chlorides alongwith the evolution of, , 2K()2HCl(aq), , ZnCl2(aq) + Ha(g), Zinc chloride, , hydrogen gas., , Thus, the order of reactivity of different, , Potassium Hydrochloric, acid, , Hydrochloric acid, , (vi) Iron reacts very slowly with dilute, hydrochloric acid giving iron (II) chloride and, , metals towards water may be written as:, , Cu >.Ag> Au, , Hydrogen, , (v) Zinc reacts slowly with dilute, hydrochloric acid to form zinc chloride and, , Hydrochloric, , K>Na>Ca>Mg> Al> Zn> Fè > Pb>, , Aluminium, chloride, , Hydrochloriç, , +H2g), CaCl2(ag)+, Calcium Hydrogen, chloride, , (ii) Magnesium reacts quite 'rapidly but, , the reaction is less vigorous than with calcium., , Cium and magnesium combine with chlorine, , even at room temperature whereas less reac, tive metals like zinc,, iron, aluminium and, copper combine with chlorine on heating., (a) Reactions occurring at room temperd", , ture, , 2Na(s) + Clz(g)Sodium, , Chlorine, , 2NaCl(s), , Sodium chloride, , Ca(s)+Cl2(g)> CaCl2(s), , Calcium, , Calcium chloride

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Mg(s)+Cl2(g)-, , MgCl2(s), , Corrosion, Corrosion is the action of atmospheric, of other gases, on, oxygen (oxidation), also, , Magnesium chloride, , Megnesium, , b)Reactions occurring on heating:, Zn(s)+Cl2(s)> ZnCl2(s), , 2Fe(s)+ 3Cl2(g) 2FeCla(s), Iron, , 2Al(s), , +, , Aluminium, , Chlorine, , Iron (II) chloride, , 3Cl2tg), Chlorine, , 2AICl3(s), , Chlorine, , Only, , combine, , potassium, calcium and magnesium, with hydrogen to form compounds called, metal hydrides. These are generally formed, Dy passing hydrogen gas, , over,, , the heated, , Heat, , 2Na(s)+H2(g)-, , Calcium Hydrogen, , otheT, , This electrolysis is done by a cell containing, dilute sulphuric acid and making aluminium, as, object as anode. This process is known, Anodising. Gold does not tarnish a s it is, non-reactive. Thus corrosion requires both, water and air., , Galvanisation is the process used for, plating metals and non-metals with other m e, tals by electrolysis to protect them against, , metal., , Ca(s)+ H2g), , or, , of aluminium oxide is coated by electrolysis., , CuCl2(s), , Copper (II) chloride, Reaction of metals with hydrogen : Metals generally do not react with hydrogen., highly reactive metals like sodium,, Copper, , layer of oxides,, , water in .addition to atmospheric gases., causes heavy, Damage by corrosion of metals, loss. To protect the aluminium a uniform layer, , Aluminium chloride, , Cu(s)+ Cl2(g)-, , to form a, , involves atmoscompounds. Dry corrosion, corrosion involves, pheric gases only. Wet, , Zinc chloride, , Chlorine, , Zine, , metals, , 2NaH(s), , Sodium hydride, , Heat, CaH2(s), , Calcium hydride, , corrosion. Corrosion is also prevented by applying paints. Such paints are often made, , from lead or zinc. Iron is mostly galvanised, with chromium., , EXERCISE