Chapter4. Perodic Table

8/6/2019 Chapter4. Perodic Table

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Chapter 4Periodic Table of Elements


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Learning Objectives

Analyse the Periodic Table of ElementsAnalyse Group 18 elements

Analyse Group 1 elementsAnalyse Group 17 elementsAnalyse elements in a period

Understand transition elements


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A. The Periodic Table of Elements

Look at these pictures carefully.


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Why the items in the supermarket or hypermarket are arranged systematically andorderly?


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Similarly, elements are arranged systematically and orderly.


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Historical development of the Periodic Table

Antoine Lavoisier Classify substances into

metals and non-metalsUnsuccessful because

light, heat and some other compounds where notelements.

(1743-1794)


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Johann Dobereiner Introduced triads.Elements were classifiedinto groups of three

elements with samechemical propertiesThe atomic mass of middleelements was approximately

the average atomic mass of the other two elements

(1780-1849)


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John NewlandsArranged elements in order of increasing atomic mass.

Elements with similar propertiesrecurred at every eight element.This was known as the Law of OctavesFailed because only obeyed by first 17

elements only

(1837-1898)


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Lothar Meyer Plotted a graph of the atomicvolume against atomic mass.Elements with similar chemicalproperties occupied samepositions.Successful in showing theproperties of elements formed a

periodic pattern against their atomic masses.

(1830-1895)


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Dmitri MendeleevArranged the elements in order of increasing atomic mass.Successful because

--he left gaps for elements yet to bediscovered. He used the table to predictthe existence and properties of undiscovered elements

--he change the order of elements of theproperties are not similar.

(1834-1907)


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http://en.wikipedia.org/wiki/File:Mendelejevs_periodiska_system_1871.png


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Historical development of the PeriodicTable

Henry J. G. Moseley (1887-1915)

Concluded that proton number shouldbe the bases for the periodic change of chemical propertiesArranged the elements in order of increasing proton number in thePeriodic Table.
http://www.google.com.my/imgres?imgurl=http://www.glogster.com/media/4/21/1/8/21010805.jpg&imgrefurl=http://www.vegetariansplitpeasoup.com/bg-Moseley-Periodic-Table/&usg=__IljwSG2UGtnwJXH0pqICegtAdM4=&h=393&w=255&sz=15&hl=en&start=5&zoom=1&itbs=1&tbnid=57dfAVAuYuSLfM:&tbnh=124&tbnw=80&prev=/images%3Fq%3DHenry%2BG.%2BJ.%2BMoseley%26hl%3Den%26sa%3DG%26rlz%3D1T4ADSA_enMY385%26biw%3D1276%26bih%3D582%26tbm%3Disch&ei=V_C2Td-GH8vOrQest_jFDQ


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Modern Periodic Table of Elements

Elements are arranged according their increasingproton number.Vertical columns = groups (according to their number of valence electron/sHorizontal rows = periods (number of electronshells filled by electrons)


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Modern Periodic Table of Elements


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Group 18/VIII Elements

Known as noble gases/ inert gases(chemically unreactive elements)Non-metals that exist as monoatomic colourless gases.

Members :Helium (He), Xenon (Xe),Neon (Ne), Radon (Ra).

Argon (Ar),Krypton (Kr),


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Physical Properties of Group 18

Very small atomic sizes.Low melting and boiling points

Weak Van der Waals forces of attraction between atoms.

Low densitiesVery small masses but huge volumes.

Melting and boiling points of elements increasedown the Group 18.


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Uses of Group 18Elements

HeliumTo fill airships and weather balloons.

Airships


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Airships


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Airships


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Uses of Group 18 Elements

Weather balloon


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Weather

balloon


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Heliumused as artificial atmosphere in oxygen tankfor divers.

Oxygentank


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Oxygentank

U f 18


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Uses of roup 18Elements

Oxygentank


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Uses of Group 18 ElementsNeon

Advertising lights

U f G 18


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NeonUsed in aeroplane runway lights


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KryptonUsed in lasers to repair the retina of the eye.


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KryptonTo fill photographic flash lamps.


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XenonMaking electron tubes and stroboscopic lamps


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XenonUsed in bubble chambers in atomic energyreactors.

U f G 18


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RadonUsed to treat cancer


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Group 1 ElementsConsists of lithium (Li), sodium (Na), potassium

(K), rubidium (Rb), caesium (Cs) and francium(Fr).They are known as alkali metals because theyreact with water to produce alkali ne solution.


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Physical Properties of Group 1 Elements

SoftLow melting pointsLow densitiesShiny and silvery surfaceGood conductor of heatGood conductor of electricity


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Hardness, melting point andboiling of the elements decrease .


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Hardness, melting point and boiling of the elementsdecrease.

Metallic bonding in metals is caused by the attractionbetween positive ions and the sea of negative electrons

surrounding them.


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When go down Group 1, atom becomes larger. The positive nucleus gets

further away from the negative sea of electrons.

The force of attraction between the metal ionsand the sea of electrons gets weaker down thegroup.

Less energy is needed to overcome thisweakening force of attraction.


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Chemical Properties of Group 1Elements

All react with water to produce alkaline metalhydroxide solution and hydrogen gas .2X(s) + 2H 2O(l) 2XOH(aq) + H 2(g)

How to test the alkaline solution?1 542 3


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Group 1 metals + Wate
http://brainiac%20alkali%20metals.flv/http://brainiac%20alkali%20metals.flv/


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All burn in oxygen gas to produce white solidmetal oxides .4X(s) + O 2(g) 2X 2O(s)

The oxide dissolve in water to form alkaline metalhydroxide solution .X2O(s) + H 2O(l) 2XOH(aq)


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All burn in chlorine gas to produce white solidmetal chlorides .

2X(s) + Cl 2(g) 2XCl(s)

Alkali metal + water


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Alkali metal + water Alkali metal Observation Equation

Lithium (Li) Lithium moves slowly on the water surface with a soft hiss sound. Acolorless solution that turns red litmuspaper blue is formed

Sodium (Na) Sodium melts to become a smallsphere , moves rapidly and randomly onthe water surface with a soft hiss sound. A colorless solution that turnsred litmus paper blue is formed

Potassium (K) Potassium melts to become a smallsphere , burns with a lilac flame , very rapidly and randomly on the water surface with a soft hiss and pop sound. A colorless solution that turnsred litmus paper blue is formed

Alkali metals + Oxygen gas


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Alkali metals + Oxygen gasAlkali metal Observation Equation

Lithium (Li) Lithium burns slowly with a red flame andliberates white fumes which become a whitesolid on the cooling to room temperature. Thewhite solid dissolves in the water to produce acolorless solution . This solution turns redlitmus paper blue

Sodium (Na) Sodium burns rapidly and brightly with ayellow flame and liberates white fumes whichbecome a white solid on the cooling to roomtemperature. The white solid dissolves in thewater to produce a colorless solution . Thissolution turns red litmus paper blue

Potassium(K)

Potassium burns very rapidly and brightly witha lilac flame and liberates white fumes whichbecome a white solid on the cooling to roomtemperature. The white solid dissolves in thewater to produce a colorless solution . This

solution turns red litmus paper blue


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Alkali metals + Chlorine gasAlkali metal Observation Equation

Lithium (Li) Lithium burns slowly with a red flame andliberates white fumes which become a whitesolid at the end of the reaction.

Sodium (Na) Sodium burns rapidly and brightly with ayellow flame and liberates white fumes whichbecome a white solid at the end of thereaction

Potassium(K)

Potassium burns very rapidly and brightly witha lilac flame and liberates white fumes whichbecome a white solid at the end of thereaction


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Why all elements in Group 1 have samechemical properties?

Chemical reaction is all about the activity of electron/sAll the elements have one valence electron .Each of them reacts by donating one valenceelectron to form an ion with a charge of +1 toachieve stable electron arrangement.


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Reactivity of Group 1 Elements

Chemical Properties of Group 1


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Why the reactivity of elements increases down the Group 1?Atomic size of Group 1 elements increases from lithium tofrancium./ Number of shells occupied by electrons increases .Distance between the valence electron in the outermost shell andpositive 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 stableelectron arrangement.

Group 17


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Group 17Elements

Members are fluorine(F 2) , chlorine(Cl 2),bromine(Br 2), iodine(I 2), and astatine(At 2)

The elements are also known as halogens which exist as diatomic molecules .

Physical Properties of Group


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Physical Properties of Group17

They have low melting and boiling pointsbecause molecules are attracted to each other by weak van der Waals forces of attraction.

The melting and boiling points of the elementsincreases down Group 17.This change the states of elements from gas to

solid and the colour of elements from lighter colour to darker colour.


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Elements State Colour

Fluorine Gas Pale yellow

Chlorine Gas Greenish-yellowBromine Liquid Reddish-brown

Iodine Solid Purplish-black


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Why the melting and boiling points of elementsincreases down Group 17?

Molecular size/relative molecular mass of the

elements increases down Group 17.Forces of attraction betweenmolecules/Intermolecular forces of attractionincreases .

More heat is needed to overcome the stronger forcesof attraction between the molecules.


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All members have similar chemical properties but differ inthe reactivity.

React with water to form two acids

X2(g) + H

2O(l) HX(aq) + HOX(aq)

Example:

Cl2(g) + H 2O(l) HCl(aq) + HOCl(aq)

hydrochloric hypochlorousacid acid

Hypochlorous acid is a bleaching agent (bleach both blue and redlitmus paper)


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All members have similar chemical properties but differ inthe reactivity.

Halogens in gaseous state react with hot iron to form brownsolid.2Fe(s) + 3X 2(g) 2FeX 3(s)

Example:

2Fe(s) + 3Cl 2(g) 2FeCl 3(s)

solid iron(III) chloride(brown)

Chemical Properties


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Chemical Propertiesof Group 17

All members have similar chemical properties but differ in the reactivity.

Halogens react with sodium hydroxide solution to producesodium halide, sodium halate(I) and water X2 + 2NaOH(aq) NaX(aq) + NaOX(aq) + H 2O(l)

Example:

Cl2 + 2NaOH(aq) NaCl(aq) + NaOCl(aq) + H 2O(l)

Sodium chlorate(I)

Chemical Properties


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Why all halogens possess similar chemicalproperties?Chemical reaction = lose or accept electron/sAll halogens always gain one electron to achievestable octet electron arrangement.Therefore, they have similar chemical properties.

Chemical Properties


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Why chemical reactivity of halogens decreasesdown Group 17?Atomic size/number of electron occupied shells of halogens increases down Group 17.The outermost shell becomes further from thenucleus of the atom.

Strength to attract one electron into the outermostshell by the nucleus becomes weaker.Reactivity decreases.


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


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PeriodAll the atoms of the elements have three shellsoccupied with electronsThe number of valence electrons in each atomincrease from 1 to 8


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PeriodAll the elements exist as solid except chlorine andargon which are gasesThe atomic radius of elements decreases. This isdue to the increasing nuclei attraction on thevalence electrons.


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PeriodThe electronegativity of elements increases. Thisis also due to the increasing nuclei attraction onthe valence electrons and the decreases in atomic

size.


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Period

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


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PeriodUses of metalloid

Make 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 andetc.


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

Basic oxides react with acids to form salt and water Acidic oxides react with alkalis to form salt and water Amphoteric oxides react with both acids and alkalis toform salt and water.

Transition


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TransitionElements

Elements from Group 3 to Group 12 in the PeriodicTable.Common characteristics

Solid metal with shiny surface.Good conductor of heat and electricity.High melting and boiling points.

Hard, malleable and ductile.

Transition


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TransitionElements

Special characteristicsAll are metalsShow different oxidation numbers in their compoundsForm coloured ions or compoundsUse as catalysts

Form complex ions

Transition


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TransitionElements

Show different oxidation numbers in their compound

Compound Formula Oxidation number

Chromium(III) chloride Cr Cl3

+3

Potassium dichromate(VII) K 2Cr 2O 7 +6

Manganese(II) sulphate MnSO 4 +2

Manganese(VI) oxide MnO 2 +4

Potassium manganate(VII) K MnO 4 +7

Iron(II) sulphate Fe SO 4 +2

Iron(III) chloride Fe Cl3 +3

Copper(I) oxide Cu 2O +1

Copper(II) sulphate Cu SO 4 +2

Transition


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TransitionElements

Form coloured ions or compoundsElement Ion Colour

Chromium Cr 3+ Green

CrO 42- Yellow

Cr 2O 72- Orange

Manganese Mn 2+ Pale pink

MnO 4- Purple

Iron Fe 2+ Pale green

Fe 3+ Yellowish brown

Cobalt Co 2+ Pink

Nickel Ni 2+ Green

Copper Cu 2+ Blue Green

Transition


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TransitionElements

Form coloured ions or compoundsGemstone Transition metal Colour

Emerald Ni and Fe Green

Amethyst Fe and Mn Purple

Sapphire Co and Ti Blue

Ruby Cr Red

Topaz Fe Yellow

Transition


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TransitionElements

Emerald

Transition


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TransitionElements

Amethyst

Transition


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TransitionElements

Sapphire

Transition


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TransitionElements

Ruby

Transition


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TransitionElements

Topaz

Transition


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TransitionElements

As catalyst

Process Catalyst Tomanufacture

Haber Process Iron fillings, Fe Ammonia

ContactProcess

Vanadium(V)oxide, V 2O 5

Sulphuric acid

OstwaldProcess

Platinum, Pt Nitric acid

Hydrogenation Nickel, Ni Margarine

Transition


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TransitionElements

To form complex ions

Element Complex ions Formula

Iron Hexacyanoferrate(II) ion [Fe(CN)6]4-

Hexacyanoferrate(III) ion [Fe(CN) 6]3-

Chromium Hexaamina chromium(III) ion [Cr(NH 3)6]3+

Copper Tetraamina copper(II) ion [Cu(NH 3)4]2+

Tetrachlorocuprate(II) ion [CuCl 4]2-

Chapter4. Perodic Table

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