Chemistry - an illustrated guide to science (794128), страница 5
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He calledthese groups triads. Subsequently,scientists attempted to arrange all ofthe known elements into triads.1373 John NewlandsH1Li2Be3F8ClNa9KMg10Ca151617B4AlC5SiN6P11Cr12Ti13MnO7S14Fe181920213 John Newlands● In1864, English chemist JohnNewlands noticed that if the elementswere arranged in increasing order ofatomic mass, the eighth element afterany given one had similar properties.He likened this to an octave of musicand called the regularity the “law ofoctaves.”● Newlands’s arrangement worked wellfor the first 17 elements but brokedown thereafter. Consequently, it wasnot well received by other scientists.4 Lothar Meyer804 Lothar Meyer● In1870, German chemist Lothar Meyerplotted a graph of atom ic volu m eagainst atomic mass.● He found a pattern in which elementsof similar properties appeared insimilar positions on the graph.4020005101520253035Atomic number4045505560© Diagram Visual Information Ltd.Atomic volume/ cm3 mol–16026ELEMENTS AND COMPOUNDSThe periodic tableKey words1 Part of Mendeleyev’s periodic tableatomic massatomic numberelementgroupgroup 1noble gasesperiodperiodic tableGroupPeriodI1H2Li1 Mendeleyev’s periodictableIIIIIIVBeBCVVIVIINOFVIII● Themodern periodic table is basedNaMgAlSiPSCl3on that developed by Russian chemistDmitry Mendeleyev in the 1860s.● He arranged the elem en ts in order ofKCa*TiVCrMn Fe Co Niincreasing atom ic m ass.
He called thehorizontal rows periods and theCuZn**AsSeBr4vertical columns grou ps. He groupedthe elements on the basis of theirRbSrYZrNbMo*properties.Ru Rh Pd● Mendeleyev made a separate group forthose elements that did not appear toAgCdInSnSbTeI5fit the pattern. He also left spacesSpaces were left for elements that had not been discovered.
They were candium, gallium,where there was no known elementgermanium, and technetium.that fit the pattern and madepredictions about themissing elements.2 Modern Periodic Table● There were some problemswith Mendeleyev’s table. Forexample, iodine was placedafter tellurium on the basisMetalsof its chemistry, eventhough its atomic mass wasSemi-metalslower than tellurium. Also,there was no obvious placeNon-metalsfor the n oble gases. These12problems were subsequentlyHHeresolved when, in 1914,567891043LiBeBCNOFNeEnglish physicist Henry1314151617181211Moseley showed that theNaMgAlSiPSClArelements could be arranged282021222324252627193233343536313029in a pattern on the basis ofCoFeMnCrCaScVKTiKrBrSeAsGeGaZnCuNitheir atom ic n u m ber.2 The modernperiodic table© Diagram Visual Information Ltd.● Metalsoccupy positions tothe left and center, whilenon-metals are found to theright. Hydrogen is theexception to this pattern.The atomic structure ofhydrogen would indicatethat it belongs at the top leftof the table; however, it is anon-metal and has verydifferent properties fromthe grou p 1 elements.37Rb38Sr55Cs56Ba87Fr88Ra39Y40Zr41Nb42Mo43Tc44Ru45Rh46Pd47Ag48Cd49In50Sn51Sb52Te53I54Xe57- 7271Hf89- 104103Rf-73Ta74W75Re76Os77Ir78Pt79Au80Hg81Tl82Pb83Bi84Po85At86Rn105Db106Sg107Bh108Hs109Mt110Ds111Rg112 113Uub Uut114 115 116Uuq Uup Uuh57La5859CePr60Nd61Pm62Sm63Eu64Gd65Tb66Dy67Ho68Er69Tm70Yb71Lu89Ac90Th92U93Np94Pu959697Am CmBk98Cf99Es100Fm101Md102No103Lr91Pa27electronelementgroup 1ionionization energylanthanide seriesmolenucleusperiodshellfirst ion ization en ergy of anelement is the energy needed toremove a single electron from 1 m oleof atoms of the elem en t in the gaseousstate, in order to form 1 mole ofpositively charged ion s.● Reading down grou p 1, there is adecrease in the first ionizationenergies.
This can be explained byconsidering the electronicconfiguration of the elements in thegroup. Reading down, the outerelectron is further from the positivelycharged n u cleu s, and there is anincreasing number of complete shellsof inner electrons, which to someextent, shield the outer electron fromthe nucleus. The result is that lessenergy is needed to remove the outerelectron. A similar situation exists inother groups.Increase in ionizationenergy● Thereis a general increase in the firstionization energies across a period.This increase is due to electrons at thesame main energy level being attractedby an increasing nuclear charge.
Thischarge is caused by the increasingnumber of protons in the nucleus. Theincrease makes it progressively moredifficult to remove an electron; thusmore energy is needed.● The diagram illustrates this principleusing the first six periods minus thelan than ide series.Elements whose ionizationenergies are the greatest intheir periodHeNeArKrXeRnHeliumNeonArgonKryptonXenonRadon© Diagram Visual Information Ltd.6807607707608408808708901010590720700810● The540Pt Au Hg Tl Pb Bi Po At RnKey words5001170ELEMENTS AND COMPOUNDSFirst ionization energy3806 Cs Ba La Hf Ta W Re Os IrXeI1010870830710560870730800720710700680660660Y6205504005 Rb SrZr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te13501140940950760580910750740760760720650Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrV6506606304205904 K Ca Sc Ti15201250Cl ArSP10107905807405003 Na MgAl Si10002080F Ne16801310ON1400C1090B8009002 Li Be13101 H5202370HeFirst ionization energiesof the elements28ELEMENTS AND COMPOUNDSKey wordsionization energynoble gasesperiodperiodicityshellVariation of firstionization energy2,500a = 2,370First ionization energies● Theb = 2,0802,000First ionization energy/ KJ mol–1graph shows a repeating pattern,or periodicity, corresponding toreading down the periods of theperiodic table.● Within a period, it becomesincreasingly more difficult to removean electron due to the increasingnuclear charge.
The graph peaks at thelast element in each period, which is an oble gas (labeled on the graph).● The noble gases have complete outershells of electrons. This electronconfiguration provides great stability,and consequently, the noble gases arevery unreactive. Some are totallyunreactive. The first ion izationen ergies of the noble gases are veryhigh.c = 1,5001,500d = 1,350e = 1,170f1,000© Diagram Visual Information Ltd.5000010a Heliumb Neonc Argon20d Kryptone Xenonf Radon304050Atomic number6070809029ELEMENTS AND COMPOUNDSKey wordsgroupgroup 1lanthanide seriesliquidmelting pointnoble gasesperiodsolidtransition metalsMelting points● Them eltin g poin t is the point atwhich the solid and liqu id phase of asubstance is in equilibrium at a givenpressure.● In a solid, the particles are held in arigid structure by the strong forces ofattraction that exist between them.They vibrate but cannot moveposition. When a solid is heated to itsmelting point, the particles gainsufficient energy to overcome theseforces of attraction, and the particlesare able to move position.● Within grou ps of metallic elements,the melting point decreases down thegroup.
The converse is true for nonmetals, where the melting pointincreases down the group.● Reading across periods 2 and 3, theelements follow a pattern of metallicstructure, giant covalent structure, andsimple covalent structure. The meltingpoint increases until a maximum isreached with the element that exists asa giant covalent structure.● The more reactive metals in grou p 1are soft and have low melting points.Tran sition m etals (elements that havean incomplete inner electronstructure) are generally harder andhave higher melting points.● The n oble gases exist as single atomswith only weak forces of attractionbetween them. Consequently, theirmelting points are very low.● Using the first six periods minus thelan than ide series, the diagramhighlights the element with thehighest melting point in a period.Elements whose melting pointsare the greatest in their periodCSiVMoWCarbonSiliconVanadiumMolybdenumTungsten© Diagram Visual Information Ltd.–71304254271328304–391064Pt Au Hg Tl Pb Bi Po At Rn1772241027003180341029962227921725296 Cs Ba La Hf Ta W Re Os Ir–112XeI114246726102172231019661554962321156232631450Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te1852Y1522769395 Rb Sr–157–721781793730420108314551495153512441857Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrV1890166015418394 K Ca Sc Ti649983 Na Mg12781812 Li Be–2591 H63–189Cl Ar–10144SP6601410Al Si119–248–220F NeON–270C3700B2300–218–270HeMelting points of theelements °C30ELEMENTS AND COMPOUNDSKey wordselementmelting pointperiodperiodicityperiodic tableVariation of meltingpointsaMelting points3,0 0 0● Thed2,50 02,0 0 0Melting point °Cgraph shows a repeating pattern,or periodicity, corresponding toreading down the periods of theperiodic table.● The structure of periods 2 and 3with regard to the nature of theelem en ts, is:Elements having a metallic structure:m eltin g poin t increasingElements having a giant covalentstructure: melting point maximumElements having a simple covalentstructure: melting point decreasing● In general, the melting point increasesat the start of these periods,corresponding to elements that havemetallic structure.
The melting point isat maximum for elements that have agiant covalent structure (labeled onthe graph). After this, the meltingpoint rapidly falls to low values,corresponding to those elements thathave a simple covalent structure.ec1,50 0b1,0 0 050 0© Diagram Visual Information Ltd.00abcde10CarbonSiliconVanadiumMolybdenumTungsten20304050Atomic number6070809031boiling pointgasgroupgroup 1kinetic energylanthanide seriesliquidnoble gasestransition metalsboilin g poin t is the temperatureat which a liqu id becomes a gas.● The particles in a liquid are heldtogether by the strong forces ofattraction that exist between them.The particles vibrate and are able tomove around, but they are held closelytogether. When a liquid is heated to itsboiling point, the particles gain kin eticen ergy, moving faster and faster.Eventually, they gain sufficient energyto break away from each other andexist separately.
There is a largeincrease in the volume of anysubstance going from a liquid to a gas.● Within grou ps of metallic elements,the boiling point decreases down thegroup. The converse is true for nonmetals: the melting point increasesdown the group.● The more reactive metals in grou p 1have relatively low boiling points.Tran sition m etals generally have veryhigh boiling points.● The n oble gases exist as single atomswith only weak forces of attractionbetween them.
Consequently, theirboiling points are very low because ittakes relatively little energy toovercome these forces.● Using the first six periods minus thelan than ide series, the diagramhighlights the element with thehighest boiling point in a period.Elements whose boiling pointsare the greatest in their period1560174014573573080382741305297562754203457CSiVMoReCarbonSiliconVanadiumMolybdenumRhenium© Diagram Visual Information Ltd.● The9625427Boiling points4602337–62Key words1640Pt Au Hg Tl Pb Bi Po At RnELEMENTS AND COMPOUNDS6696 Cs Ba La Hf Ta W Re Os IrXeI18499017502260208076522122970372739004877556047424377Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb TeY333813846865 Rb Sr–1525968561328302403907256727302870275019622670Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrV33803287283114844 K Ca Sc Ti11078833 Na Mg297013422 Li Be–2531 H760–186–35Cl ArSP2802620Al Si2467445–246–188F NeON–196C4827B2550–183–269HeBoiling points of theelements °C32ELEMENTS AND COMPOUNDSKey wordsboiling pointgasgroup 1group 2transition metalsVariation of boilingpointscaedVariation of boiling point● Themajority of non-metallic elementsare gases at room temperature andatmospheric pressure.
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