Chapter 4Periodic Table of Elements

Learning ObjectivesAnalyse the Periodic Table of ElementsAnalyse Group 18 elementsAnalyse Group 1 elementsAnalyse Group 17 elementsAnalyse elements in a periodUnderstand transition elements

A. The Periodic Table of ElementsLook at these pictures carefully.

A. The Periodic Table of ElementsWhy the items in the supermarket or hypermarket are arranged systematically and orderly?

A. The Periodic Table of ElementsSimilarly, elements are arranged systematically and orderly.

Historical development of the Periodic TableAntoine LavoisierClassify substances into metals and non-metalsUnsuccessful because light, heat and some other compounds where not elements. (1743-1794)

Historical development of the Periodic TableJohann DobereinerIntroduced triads. Elements were classifiedinto groups of three elements with same chemical propertiesThe atomic mass of middleelements was approximatelythe average atomic mass ofthe other two elements (1780-1849)

Historical development of the Periodic TableJohn NewlandsArranged elements in order ofincreasing atomic mass.Elements with similar propertiesrecurred at every eight element.This was known as the Law ofOctavesFailed because only obeyed byfirst 17 elements only

(1837-1898)

Historical development of the Periodic TableLothar MeyerPlotted a graph of the atomic volume against atomic mass.Elements with similar chemical properties occupied same positions.Successful in showing the properties of elements formed a periodic pattern against their atomic masses. (1830-1895)

Historical development of the Periodic TableAntoine LavoisierClassify substances into metals and non-metalsUnsuccessful because light, heat and some other compounds where not elements.

(1834-1907)

Historical development of the Periodic TableHenry J. G. Moseley (1887-1915)Concluded that proton number should be the bases for the periodic change of chemical propertiesArranged the elements in order of increasing proton number in the Periodic Table.

Modern Periodic Table of ElementsElements are arranged according their increasing proton number.Vertical columns = groups(according to their number of valence electron/sHorizontal rows = periods (number of electron shells filled by electrons)

Modern Periodic Table of Elements

Group 18/VIII ElementsKnown as noble gases/inert gases(chemically unreactive elements)Non-metals that exist as monoatomic colourless gases. Members : Helium(He), Neon(Ne), Argon(Ar), Krypton(Kr), Xenon(Xe), Radon(Ra).

Physical Properties of Group 18Very small atomic sizes. Low melting and boiling pointsWeak van der Waals forces of attraction between atoms. Low densitiesVery small masses but huge volumes. Melting and boiling points of elements increase down the Group 18.

Chemical Properties?All Group 18 elements are chemically inert/unreactive. The outermost electron shell of each member is fully occupied by electrons. This is a stable electron arrangement which inHelium, it is said achieve duplet electron arrangement.Other than Helium, it is said achieve octet electron arrangement.

Uses of Group 18 ElementsHeliumTo fill airships and weather balloons. Airships

Uses of Group 18 ElementsHeliumTo fill airships and weather balloons. Airships

Uses of Group 18 ElementsHeliumTo fill airships and weather balloons. Airships

Uses of Group 18 ElementsHeliumTo fill airships and weather balloons. Weatherballoon

Uses of Group 18 ElementsHeliumTo fill airships and weather balloons. Weatherballoon

Uses of Group 18 ElementsHeliumused as artificial atmosphere in oxygen tank for divers.Oxygen tank

Uses of Group 18 ElementsHeliumused as artificial atmosphere in oxygen tank for divers.Oxygen tank

Uses of Group 18 ElementsHeliumused as artificial atmosphere in oxygen tank for divers.Oxygen tank

Uses of Group 18 ElementsNeonAdvertising lights

Uses of Group 18 ElementsNeonUsed in aeroplane runway lights

Uses of Group 18 ElementsArgonTo fill light bulbs.

Uses of Group 18 ElementsKryptonUsed in lasers to repair the retina of the eye.

Uses of Group 18 ElementsKryptonTo fill photographic flash lamps.

Uses of Group 18 ElementsXenonMaking electron tubes and stroboscopic lamps

Uses of Group 18 ElementsXenonUsed in bubble chambers in atomic energy reactors.

Uses of Group 18 ElementsRadonUsed to treat cancer

Group 1 ElementsConsists of lithium(Li), sodium(Na), potassium(K), rubidium(Rb), caesium(Cs) and francium(Fr). They are known as alkali metals because they react with water to produce alkaline solution.

Physical Properties of Group 1 ElementsSoft Low melting pointsLow densitiesShiny and silvery surfaceGood conductor of heatGood conductor of electricity

Physical Properties of Group 1 ElementsHardness, melting point and boiling of the elements decrease.

Physical Properties of Group 1 ElementsHardness, melting point and boiling of the elements decrease. Metallic bonding in metals is caused by the attraction between positive ions and the sea of negative electrons surrounding them.

Physical Properties of Group 1 ElementsHardness, melting point and boiling of the elements decrease. When go down Group 1, atom becomes larger. The positive nucleus gets further away from the negative sea of electrons.

Physical Properties of Group 1 ElementsHardness, melting point and boiling of the elements decrease. The force of attraction between the metal ions and the sea of electrons gets weaker down the group.

Physical Properties of Group 1 ElementsHardness, melting point and boiling of the elements decrease. Less energy is needed to overcome this weakening force of attraction.

Chemical Properties of Group 1 ElementsAll react with water to produce alkaline metal hydroxide solution and hydrogen gas. 2X(s) + 2H2O(l) 2XOH(aq) + H2(g)How to test the alkaline solution?

Group 1 metals + Water

Group 1 metals + Water

Group 1 metals + Water

Chemical Properties of Group 1 ElementsAll burn in oxygen gas to produce white solid metal oxides. 4X(s) + O2(g) 2X2O(s)The oxide dissolve in water to form alkaline metal hydroxide solution.X2O(s) + H2O(l) 2XOH(aq)

Chemical Properties of Group 1 ElementsAll burn in chlorine gas to produce white solid metal chlorides.2X(s) + Cl2(g) 2XCl(s)

Chemical Properties of Group 1 ElementsWhy all elements in Group 1 have same chemical properties?Chemical reaction is all about the activity of electron/sAll the elements have one valence electron.Each of them reacts by donating one valence electron to form an ion with a charge of +1 to achieve stable electron arrangement.

Chemical Properties of Group 1 ElementsWhy the reactivity of elements increases down the Group 1?Atomic size of Group 1 elements increases from lithium to francium./Number of shells occupied by electrons increases.Distance between the valence electron in the outermost shell and positive nucleus increases down the Group 1. Attraction between nucleus and valence electron decreases.It is easier for the atom to lose the valence electron to achieve stable electron arrangement.

Group 1 metals + Water

Group 17 ElementsMembers are fluorine(F2) , chlorine(Cl2), bromine(Br2), iodine(I2), and astatine(At2) The elements are also known as halogens which exist as diatomic molecules.

Physical Properties of Group 17They have low melting and boiling points because molecules are attracted to each other by weak van der Waals forces of attraction. The melting and boiling points of the elements increases down Group 17.This change the states of elements from gas to solid and the colour of elements from lighter colour to darker colour.

Physical Properties of Group 17

ElementsStateColourFluorineGasPale yellowChlorineGasGreenish-yellowBromineLiquidReddish-brownIodineSolidPurplish-black

Physical Properties of Group 17Why the melting and boiling points of elements increases down Group 17?Molecular size/relative molecular mass of the elements increases down Group 17.Forces of attraction between molecules/Intermolecular forces of attraction increases.More heat is needed to overcome the stronger forces of attraction between the molecules.

Chemical Properties of Group 17All members have similar chemical properties but differ in the reactivity.React with water to form two acidsX2(g) + H2O(l) HX(aq) + HOX(aq)Example: Cl2(g) + H2O(l) HCl(aq) + HOCl(aq) hydrochloric hypochlorous acid acidHypochlorous acid is a bleaching agent (bleach both blue and red litmus paper)

Chemical Properties of Group 17All members have similar chemical properties but differ in the reactivity.Halogens in gaseous state react with hot iron to form brown solid. 2Fe(s) + 3X2(g) 2FeX3(s)Example:2Fe(s) + 3Cl2(g) 2FeCl3(s) solid iron(III) chloride(brown)

Chemical Properties of Group 17All members have similar chemical properties but differ in the reactivity.Halogens react with sodium hydroxide solution to produce sodium halide, sodium halate(I) and waterX2 + 2NaOH(aq) NaX(aq) + NaOX(aq) + H2O(l)Example:Cl2 + 2NaOH(aq) NaCl(aq) + NaOCl(aq) + H2O(l) Sodium chlorate(I)

Chemical Properties of Group 17Why all halogens possess similar chemical properties?Chemical reaction = lose or accept electron/sAll halogens always gain one electron to achieve stable octet electron arrangement. Therefore, they have similar chemical properties.

Chemical Properties of Group 17Why chemical reactivity of halogens decreases down Group 17?Atomic size/number of electron occupied shells of halogens increases down Group 17.The outermost shell becomes further from the nucleus of the atom.Strength to attract one electron into the outermost shell by the nucleus becomes weaker.Reactivity decreases.

PeriodElements across a period exhibit a periodic change in properties.Period 3Proton number increases by one unit from one element to the next element

PeriodAll the atoms of the elements have three shells occupied with electronsThe number of valence electrons in each atom increase from 1 to 8

PeriodAll the elements exist as solid except chlorine and argon which are gasesThe atomic radius of elements decreases. This is due to the increasing nuclei attraction on the valence electrons.

PeriodThe electronegativity of elements increases. This is also due to the increasing nuclei attraction on the valence electrons and the decreases in atomic size.

Period

Metals Metalloid Non-metalsMetalloid semi-metal, reacts with acid only, weak conductor, brittle and not malleable and ductile.

PeriodUses of metalloidMake diodes and transistorsA diode A transistor

Both are commonly used in the making of microchipsMicrochips are widely used in the manufacture of computers, mobile phones, televisions, video recorders, calculators, radio and etc.

PeriodOxides of elements change from basic to amphoteric and then to acidic across the period towards the right.

Basic oxides react with acids to form salt and waterAcidic oxides react with alkalis to form salt and waterAmphoteric oxides react with both acids and alkalis to form salt and water.

Transition ElementsElements from Group 3 to Group 12 in the Periodic Table.Common characteristicsSolid metal with shiny surface. Good conductor of heat and electricity.High melting and boiling points.Hard, malleable and ductile.

Transition ElementsSpecial characteristicsShow different oxidation numbers in their compoundsForm coloured ions or compoundsUse as catalystsForm complex ions

Transition ElementsShow different oxidation numbers in their compound

CompoundFormulaOxidation numberChromium(III) chlorideCrCl3+3Potassium dichromate(VII)K2Cr2O7+6Manganese(II) sulphateMnSO4+2Manganese(VI) oxideMnO2+4Potassium manganate(VII)KMnO4+7Iron(II) sulphateFeSO4+2Iron(III) chlorideFeCl3+3Copper(I) oxideCu2O+1Copper(II) sulphateCuSO4+2

Transition ElementsForm coloured ions or compounds

ElementIonColourChromiumCr3+GreenCrO42-YellowCr2O72-OrangeManganeseMn2+Pale pinkMnO4-PurpleIronFe2+Pale greenFe3+Yellowish brownCobaltCo2+PinkNickelNi2+Green

CopperCu2+Blue Green

Transition ElementsForm coloured ions or compounds

GemstoneTransition metalColourEmeraldNi and FeGreenAmethystFe and MnPurpleSapphireCo and TiBlueRubyCrRedTopazFeYellow

Transition ElementsEmerald

Transition ElementsAmethyst

Transition ElementsSapphire

Transition ElementsRuby

Transition ElementsTopaz

Transition ElementsAs catalyst

ProcessCatalystTo manufactureHaber ProcessIron fillings, FeAmmoniaContact ProcessVanadium(V) oxide, V2O5Sulphuric acidOstwald ProcessPlatinum, PtNitric acidHydrogenationNickel, NiMargarine

Transition ElementsTo form complex ions

ElementComplex ionsFormulaIronHexacyanoferrate(II) ion[Fe(CN)6]4-Hexacyanoferrate(III) ion[Fe(CN)6]3-ChromiumHexaamina chromium(III) ion[Cr(NH3)6]3+CopperTetraamina copper(II) ion[Cu(NH3)4]2+Tetrachlorocuprate(II) ion[CuCl4]2-

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