化学专业英语《Chemistry English》课程教学资源（讲义）A MS Word version of Lectures1-12 is available for you to make print copy

Chemistry EnglishFor 1st-year undergraduate students of CCCEByXinLu（吕鑫)E-mail:xinlu@xmu.edu.cnTel:2181600 (Office)5916410(Home)http://pcssl.xmu.edu.cn/~xinlu/C6o (Fullerene)Carbon NanotubeTwo hottest allotropic forms of carbon

Chemistry English For 1st -year undergraduate students of CCCE By Xin Lu (吕鑫) E-mail: xinlu@xmu.edu.cn Tel: 2181600 (Office) 5916410(Home) http://pcss1.xmu.edu.cn/~xinlu/ • Two hottest allotropic forms of carbon C60 (Fullerene) Carbon Nanotube

Outline.SomeAspects ofGeneralChemistry(~7 times).SomeAspects ofOrganicChemistry (~4times)·SomeAspectsof Biochemistry(~2 times)URL ofthis course: http:/pcssl.xmu.edu.cn/-xinlu/courses/ce/Reference Books**IntroductiontoGeneral,OrganicandBiologicalChemistrybySallySolomon,McGraw-Hill BookCompany.《科技英语选读：化学化工·材料应用物理》，主编：马翎，外文出版社。Chemical&EngineeringNews(Weekly),AmericanChemicalSociety.1

1 Outline • Some Aspects of General Chemistry ( ~ 7 times) • Some Aspects of Organic Chemistry ( ~ 4 times) • Some Aspects of Biochemistry ( ~2 times) URL of this course: http://pcss1.xmu.edu.cn/~xinlu/courses/ce/ Reference Books • **Introduction to General, Organic and Biological Chemistry by Sally Solomon, McGraw-Hill Book Company. • 《科技英语选读：化学化工•材料•应用物理》，主编：马翎，外文出版社。 • Chemical & Engineering News (Weekly), American Chemical Society

ContentChapter1MeasurementsNChapter2-5Matter and EnergyChapter3Atoms7Chapter412ChemicalBondingChapter5-18Gases and AtmosphereChapter6--20Liquids and Solids23Chapter7Solutions-28Chapter8ChemicalReactions-32Chapter9Acids and Bases-35Chapter10Alkanes38Chapter 11Alkenes and Alkynes40Chapter 12Benzenes and TheAromaticHydrocarbonsChapter 13- 43Alcohols and Ethes-- 45Chapter 14Aldehydes andKetonesChapter15CarboxylicAcidsandDerivatives48Chapter16Amines,OtherNitrogen Compoundsand Organic Sulfur49Compounds53Chapter17SyntheticPolymers56Chapter18CarbohydratesChapter 1959Proteins科技英语论文写作Chapter20--612

2 Content Chapter 1 Measurements ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 3 Chapter 2 Matter and Energy ┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 5 Chapter 3 Atoms ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 7 Chapter 4 Chemical Bonding ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 12 Chapter 5 Gases and Atmosphere ┄┄┄┄┄┄┄┄┄┄┄┄┄ 18 Chapter 6 Liquids and Solids ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 20 Chapter 7 Solutions ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 23 Chapter 8 Chemical Reactions ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 28 Chapter 9 Acids and Bases ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 32 Chapter 10 Alkanes ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 35 Chapter 11 Alkenes and Alkynes ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 38 Chapter 12 Benzenes and The Aromatic Hydrocarbons ┄┄┄ 40 Chapter 13 Alcohols and Ethes ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 43 Chapter 14 Aldehydes and Ketones ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 45 Chapter 15 Carboxylic Acids and Derivatives ┄┄┄┄┄┄┄┄┄ 48 Chapter 16 Amines, Other Nitrogen Compounds and Organic Sulfur Compounds ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 49 Chapter 17 Synthetic Polymers ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 53 Chapter 18 Carbohydrates ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 56 Chapter 19 Proteins ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 59 Chapter 20 科技英语论文写作 ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄ 61

Chapter 1Measurements1.1IntroductionFrom simple chemicals the modem chemist can synthesize a drug with the ideal structural features totreat a particular disease or create a remarkable plastic with just the right properties to replace a wombody part.Very rarely does a sudden, almost magical, discovery lead the way to this sort of success.Inmostcasescareful,occasionallytedious,experimentationmustcomefirst.Perfoming experiments in chemistry and interpreting their results is what chemists do. It is with thedevices used to produce measured quantities, the units in which they are expressed, and the techniquesusedtodocalculations uponthem thatthe studyofchemistry begins1.2ExperimentsChemical experiments fall into two broad categories, qualitative experiments and quantitativeexperiments.In qualitative experiments, the presence or absence of some physical quantity is noted.Inquantitative experiments, the physical quantities aremeasured to see how muchofit there is.For example, in the experiments to testfor glucose in urine, a Qualitative observation shows that thesample contains glucose, whereas a Quantitative observation shows that the sample contains 10mg ofglucose.1.3Units and the SI SystemA unit describesa physical quantity that is being measured, e.g. 10 mgofglucoseApractical and useful setofunits must be internationallyaccepted and unambiguouslydefinedThree sets of units in use are:a)English System: e.g.,foot and pound, rarely used in scientific studiesb)Metric system: e.g.,meter and kilogram units, widely adopted.International SystemofUnits (SISystem)c)1.4SIUnitsSIunits werecreated in1969,inordertoclear upanypossibleconfusionaboutwhichunits shouldbe included in the modern metric system.SI Units includes the SI base units, the SI derived units,andthe SI prefixes.SI base units: There are seven SI base units for length, mass, time, amount of substance,temperature,electric current and luminous intensity,respectively.Theyare listed in the Table followingPhysical QuantityName of UnitAbbreviationLengthmetermMasskgkilogramTimesecondsmolemolAmountof substanceKkelvinTemperatureAElectric currentamperecdLuminous intensitycandela3

3 Chapter 1 Measurements 1.1 Introduction From simple chemicals the modern chemist can synthesize a drug with the ideal structural features to treat a particular disease or create a remarkable plastic with just the right properties to replace a worn body part. Very rarely does a sudden, almost magical, discovery lead the way to this sort of success. In most cases careful, occasionally tedious, experimentation must come first. Performing experiments in chemistry and interpreting their results is what chemists do. It is with the devices used to produce measured quantities, the units in which they are expressed, and the techniques used to do calculations upon them that the study of chemistry begins. 1.2 Experiments Chemical experiments fall into two broad categories, qualitative experiments and quantitative experiments. In qualitative experiments, the presence or absence of some physical quantity is noted. In quantitative experiments, the physical quantities are measured to see how much of it there is. For example, in the experiments to test for glucose in urine, a Qualitative observation shows that the sample contains glucose, whereas a Quantitative observation shows that the sample contains 10mg of glucose. 1.3 Units and the SI System A unit describes a physical quantity that is being measured, e.g. 10 mg of glucose. A practical and useful set of units must be internationally accepted and unambiguously defined. Three sets of units in use are: a) English System: e.g., foot and pound, rarely used in scientific studies. b) Metric system: e.g., meter and kilogram units, widely adopted. c) International System of Units(SI System). 1.4 SI Units SI units were created in 1969, in order to clear up any possible confusion about which units should be included in the modern metric system. SI Units includes the SI base units, the SI derived units, and the SI prefixes. SI base units: There are seven SI base units for length, mass, time, amount of substance, temperature, electric current and luminous intensity, respectively. They are listed in the Table following. Physical Quantity Name of Unit Abbreviation Length meter m Mass kilogram kg Time second s Amount of substance mole mol Temperature kelvin K Electric current ampere A Luminous intensity candela cd

SIPrefixes:The ninewidelyused SI prefixes arelisted in thefollowing tablePrefixMeaningAbbreviationpicop10-12 (one-trillionth)n10-9 (one-billionth)nano10-6 (one-millionth)microμmillim10-3 (one-thousandth)c10-2 (one-hundredth)centiddeci10-" (one-tenth)kkilo103 (one thousand times)M10° (onemillion times)megaSI Derived UnitsSI derived units are in form of combinations of SI base units and, sometimes, SI Prefixes.Forexample,VolumeunitsareSIderivedunitsvolumeunit=(lengthunit)31cm3=1ml(milliliter)Idm3=1L(liter)ContainersthatareusedinchemicallaboratoriestomeasurevolumeincludeBeaker（量杯，烧杯）Graduated cylinder（量筒），Burette（滴管），Syringe(注射器），Measuringpipet（吸量管）Transferpipet(移液管),andVolumetricflask(容量瓶)Another SI derivedunitisforDensitywhichisthecombinationofmassandvolumeunitsDensity=mass/volumeWater: 1.0g/cm3(1g/ml)Gold: 19.3g/cm3(19.3g/ml)4

4 SI Prefixes: The nine widely used SI prefixes are listed in the following table. Prefix Abbreviation Meaning pico p 10-12 (one-trillionth) nano n 10-9 (one-billionth) micro  10-6 (one-millionth) milli m 10-3 (one-thousandth) centi c 10-2 (one-hundredth) deci d 10-1 (one-tenth) kilo k 103 (one thousand times) mega M 106 (one million times) SI Derived Units SI derived units are in form of combinations of SI base units and, sometimes, SI Prefixes. For example, Volume units are SI derived units. volume unit =(length unit)3 1 cm3 = 1 ml (milliliter) 1 dm3 = 1 L (liter) Containers that are used in chemical laboratories to measure volume include Beaker (量杯, 烧杯), Graduated cylinder (量筒), Burette (滴管), Syringe(注射器), Measuring pipet (吸量管 ), Transfer pipet(移液管),and Volumetric flask(容量瓶). Another SI derived unit is for Density which is the combination of mass and volume units. Density = mass/volume Water: 1.0 g/cm3 (1 g/ml) Gold: 19.3 g/cm3 (19.3 g/ml)

Chapter 2Matterand Energy2.1 IntroductionMatter is anything that has mass and occupies space, e.g, a drink of water, a chunk of metal or evena breath ofair. Chemists study matter from one particular point of view, ie., they explain the behavior ofmatter in tems of the invisible buildingblocks of which it is made.Atoms are the indivisible,discreteparticlesofwhich all matter is composed.Molecules are collectionsofatoms which are heldtogetherbylinkscalledchemicalbonds.2.2Chemical Properties ofMatterA chemical property describes the ability of a substance to undergo a chemical change. Achemicalchange occurs when the atoms of a substance rearrange by bond breaking and bond formation toproduce a new substancethat is chemicallydifferent from the original ones.When such chemicalchanges occur, a chemical reaction is said to have taken place.The original substances are calledreactants andthenewonesarecalledproducts.Chemistsdescribechemical reactionsbyusinganarrowpointingfromthereactantstotheproductsReactants-→products.Examplesofchemical changes:burning,andcorrosion.2.3PhysicalPropertiesof MatterWhen a substance undergoes a plysical change,no chemical bonds are fomed or broken and nochemical reaction takes place.The molecules and atoms of the original substance are the same before andafter the physical change. Some important physical properties are color, density,boiling point andfreezing point.2.4 States of Matter and Physical ChangesOne physical property which is readily observed is the physical state,that is, whether something is asolid, a liquid, or a gas (at a given temperature and pressure).Melting: the process that a solid is transformed into a liquid by applying heat to it.Freezing:thereverseprocess of meltingby coolinga liquidVaporization:the process thata liquid is converted into a gas by heating2.5 Types of MatterElements:An element is a pure substance which consists of just onekindofatom.The106different elements on earth arelisted in the Periodic Table ofelements.Compounds: A compound is a pure substance which contains just onekind ofmoleculeMixtures includemorethan one puresubstance,which canbe separatedfrom eachother withoutachemicalreaction.2.6Law of Conservation of MatterRegardless ofwhat chemical reaction takes place,careful weighings showthatthemassofreactantsisalwaysexactlythesameasthemassofproducts.Masscannotbecreated ordestroyed,aprincipleknownasthelawofconservationofmatter.5

5 Chapter 2 Matter and Energy 2.1 Introduction Matter is anything that has mass and occupies space, e.g., a drink of water, a chunk of metal or even a breath of air. Chemists study matter from one particular point of view, i.e., they explain the behavior of matter in terms of the invisible building blocks of which it is made. Atoms are the indivisible, discrete particles of which all matter is composed. Molecules are collections of atoms which are held together by links called chemical bonds. 2.2 Chemical Properties of Matter A chemical property describes the ability of a substance to undergo a chemical change. A chemical change occurs when the atoms of a substance rearrange by bond breaking and bond formation to produce a new substance that is chemically different from the original ones. When such chemical changes occur, a chemical reaction is said to have taken place. The original substances are called reactants and the new ones are called products. •Chemists describe chemical reactions by using an arrow pointing from the reactants to the products: Reactants → products. Examples of chemical changes: burning, and corrosion. 2.3 Physical Properties of Matter When a substance undergoes a physical change, no chemical bonds are formed or broken and no chemical reaction takes place. The molecules and atoms of the original substance are the same before and after the physical change. Some important physical properties are color, density, boiling point and freezing point. 2.4 States of Matter and Physical Changes One physical property which is readily observed is the physical state, that is, whether something is a solid, a liquid, or a gas(at a given temperature and pressure). Melting: the process that a solid is transformed into a liquid by applying heat to it. Freezing: the reverse process of melting by cooling a liquid. Vaporization: the process that a liquid is converted into a gas by heating. 2.5 Types of Matter Elements: An element is a pure substance which consists of just one kind of atom. The 106 different elements on earth are listed in the Periodic Table of elements. Compounds: A compound is a pure substance which contains just one kind of molecule. Mixtures include more than one pure substance, which can be separated from each other without a chemical reaction. 2.6 Law of Conservation of Matter Regardless of what chemical reaction takes place, careful weighings show that the mass of reactants is always exactly the same as the mass of products. Mass can not be created or destroyed, a principle known as the law of conservation of matter

2.7EnergyEnergy is defined as the ability to do work. Whirling tornadoes, rushing streams, and movingpeople are all sources ofenergy. The energy that involves objects in motion is called kinetic energyStored energy is calledpotentialenergy,e.g,thewaterbehind a dam.Chemicalenergy is theenergychangethataccompanieschemicalreactions.Law of ConservationofEnergyThe law ofconservationof energy states energy is neither created nor destroyed,but may bechangedinform.2.8Units ofEnergyThe SI energy unit is Joule,abbreviated J,a derived unit which is a combinationofthekilogram,meter, and second1J=1kgm2s2Chemists and biochemists sometimes substitute the non-SI energy unit calorie (cal):1cal=4.184JAssignment1Writean article (at least200words)withoneofthefollowingtwotopicsa)Why isChemistry Interesting?Whyis it necessaryforyouChinesechemical studentsto learnChemistryEnglish?Completingbothwill be highlyappreciated!6

6 2.7 Energy Energy is defined as the ability to do work. Whirling tornadoes, rushing streams, and moving people are all sources of energy. The energy that involves objects in motion is called kinetic energy. Stored energy is called potential energy, e.g., the water behind a dam. Chemical energy is the energy change that accompanies chemical reactions. Law of Conservation of Energy The law of conservation of energy states energy is neither created nor destroyed, but may be changed in form. 2.8 Units of Energy The SI energy unit is Joule, abbreviated J, a derived unit which is a combination of the kilogram, meter, and second: 1 J = 1 kg m2 s -2 Chemists and biochemists sometimes substitute the non-SI energy unit calorie (cal): 1 cal = 4.184 J Assignment 1 a) Write an article (at least 200 words) with one of the following two topics: Why is Chemistry Interesting? Why is it necessary for you Chinese chemical students to learn Chemistry English? Completing both will be highly appreciated!

Chapter 3Atoms3.1 IntroductionIn Greek atomos means"indivisible"Atomictheory:if thematter weredivided a sufficientnumber of times,itcouldeventuallybereducedtothe indivisible,indestructibleparticlescalledatomThe atomic theory was presented by the British chemist John Dalton (1766-1844) in the early 1800sIt is one of the greatest advances in the history of chemistry."Whether matter be atomic or not, thismuch is certain, that granting it to be atomic, it would appear as it now does."(by Micheal Faraday(1794-1867) and J.B. Dumas(1800-1884). The main points of the Atomic Theory include: 1) Theultimate particles of elements are atoms; 2) Atoms are indestructible; 3) Elements consist of only onekind of atom; 4) Atoms of different elements differ in mass and in other properties; 5)Compounds consistofmolecules(whichDaltoncalledcompoundatoms")whichformfromsimpleandfixedcombinationofdifferentkinds ofatoms.Drawbacks of the Atomic Theory: Points 2 and 3 of Dalton's Atomic Theory do not agree withmodern experimental evidence because atoms can be broken down and atoms of one particular elementcandifferinmass3.2ElementSymbolsWith the discovery of atoms came the chemical alphabet of element symbols. Dalton chose the circleas the symbol for oxygen and represented all other elements byvariations of the circle.These earlyprimitive symbolsevolved into the modern system of using one or twoletters ofthe English alphabet.Modern system ofelement symbols: The first letter is always a capital and the second, if there is one,a lower case.The symbols are often formed from the first letter of the element name or from the firstletter along with oneother.e.g,Bstandsfor the elementboron, Ba forbarium,Befor beryllium,and Bkfor berkelium(铬,belongsto theActinium(钢)series.)Exceptions: For some of 106 elements it is not possible to guess the symbol by examining theEnglish name. For instance, the symbol for the element iron is Fe (not I or Ir) Iron, along with copper,silver,gold, sodium,potassium,lead, tin, antimony,and tungsten have symbols thatarederived from oneor twoletters oftheir Latin orGerman names.3.3FormulasThe fomulas used to represent compounds and elements inlcude element symbols and subscripts,e.g.H,Orepresents awatermolecule3.4SubatomicparticlesParticles smaller than even the smallest atoms are called subatomic particles.They are Electron(1870s),Proton(later1800s)andNeutron(1930s)3.5Atomic mass unit (amu)It isdifficult to comprehend how incredibly small arethemasses of subatomic particles.e.g.Protonmass=1.673X10-24gNeutron mass=1.673 × 10-24gElectronmass =9.11 X 10-28 g7

7 Chapter 3 Atoms 3.1 Introduction In Greek atomos means “indivisible”. Atomic theory: if the matter were divided a sufficient number of times, it could eventually be reduced to the indivisible, indestructible particles called atom. The atomic theory was presented by the British chemist John Dalton (1766-1844) in the early 1800s. It is one of the greatest advances in the history of chemistry. “Whether matter be atomic or not, this much is certain, that granting it to be atomic, it would appear as it now does.”(by Micheal Faraday (1794-1867) and J.B. Dumas(1800-1884)). The main points of the Atomic Theory include: 1) The ultimate particles of elements are atoms; 2) Atoms are indestructible; 3) Elements consist of only one kind of atom; 4) Atoms of different elements differ in mass and in other properties; 5) Compounds consist of molecules (which Dalton called “compound atoms”), which form from simple and fixed combination of different kinds of atoms. Drawbacks of the Atomic Theory: Points 2 and 3 of Dalton’s Atomic Theory do not agree with modern experimental evidence because atoms can be broken down and atoms of one particular element can differ in mass. 3.2 Element Symbols With the discovery of atoms came the chemical alphabet of element symbols. Dalton chose the circle as the symbol for oxygen and represented all other elements by variations of the circle. These early primitive symbols evolved into the modern system of using one or two letters of the English alphabet. Modern system of element symbols: The first letter is always a capital and the second, if there is one, a lower case. The symbols are often formed from the first letter of the element name or from the first letter along with one other. e.g., B stands for the element boron, Ba for barium, Be for beryllium, and Bk for berkelium.(锫, belongs to the Actinium(锕) series.) Exceptions: For some of 106 elements it is not possible to guess the symbol by examining the English name. For instance, the symbol for the element iron is Fe (not I or Ir). Iron, along with copper, silver, gold, sodium, potassium, lead, tin, antimony, and tungsten have symbols that are derived from one or two letters of their Latin or German names. 3.3 Formulas The formulas used to represent compounds and elements inlcude element symbols and subscripts,e.g. H2O represents a water molecule. 3.4 Subatomic particles Particles smaller than even the smallest atoms are called subatomic particles. They are Electron (1870s) , Proton (later 1800s) and Neutron (1930s). 3.5 Atomic mass unit (amu) It is difficult to comprehend how incredibly small are the masses of subatomic particles. e.g. Proton mass = 1.673 × 10-24 g Neutron mass = 1.673 × 10-24 g Electron mass = 9.11 × 10-28 g

Quoting the masses ofthese particles in grams is definitely awkward. A convenient unit to use is theatomic mass unit1 amu=1.66057 × 10-24g3.6AtomicNumberZThe identity of an element depends on the number of protons in the nuclei of its atoms. The numberofprotons in the nucleus ofan atom is called theatomic number of the atom,labeled Z.All atoms of thesame element must have the same number of protons. The number of positively charged protons and thenumberof negativelychargedelectrons inanatommustbethe same.3.7 Isotopes andMass NumbersThe sum of the number of protons and the number of neutrons in the nucleus of an atom is the massnumber.(A=Z +N).Atoms of the same element can have a different number of neutrons intheir nuclei.Isotopes are atoms of the sameelement which contain a different number of neutrons andthushavedifferentmass numbers.TableIsotopes of Oxygen and ChlorinepneIsotopeNatural Abundance,%888160or0-1699.76170 or 0-178980.0488180or0-18100.2035Clor CI-3517181775.5337Clor CI-3717201724.473.8Atomic WeightDalton recognized the hopelessness of ascertaining the absolute weights of atoms because atoms aremuchtoosmalltobeweighted.ItispossibletocomparetheweightsofalargenumberofatomsofelementAwiththatofthesamenumberofatomsofelementB.AtomicWeightsforelementsaredetermined by comparing a very large number of the atoms ofthe element with the same number ofatoms of C-12. By definition the atomic weight ofC-12 is exactly 12.For instance, the atomic weight ofH is 1.008, meaning that H atoms are about one-twelfth as heavy as C-12 atoms.CalculatingtheatomicweightThe atomic weight of an elementis the weighted average ofthe atomic weights ofall its naturalisotopesandcanbecalculatediftheatomicweightsandrelativeabundancesoftheisotopesaregivenE.g.,Thereare two naturallyoccurringchlorine isotopes,Cl-35and Cl-37,with relativeabundancesof 75.5% and 24.5%, respectively.AtomicWeightCl=(0.755X35.0)+(0.245X37.0)Atomic WeightCl=35.53.9Formula WeightThe formula weight of an element or compound is calculated by adding the atomic weights alltheatoms in its formula.8

8 Quoting the masses of these particles in grams is definitely awkward. A convenient unit to use is the atomic mass unit. 1 amu = 1.66057 × 10-24 g 3.6 Atomic Number Z The identity of an element depends on the number of protons in the nuclei of its atoms. The number of protons in the nucleus of an atom is called the atomic number of the atom, labeled Z. All atoms of the same element must have the same number of protons. The number of positively charged protons and the number of negatively charged electronsin an atom must be the same. 3.7 Isotopes and Mass Numbers The sum of the number of protons and the number of neutrons in the nucleus of an atom is the mass number. ( A = Z + N ). Atoms of the same element can have a different number of neutrons in their nuclei. Isotopes are atoms of the same element which contain a different number of neutrons and thus have different mass numbers. Table Isotopes of Oxygen and Chlorine Isotope p n e Natural Abundance, % 16O or O-16 8 8 8 99.76 17O or O-17 8 9 8 0.04 18O or O-18 8 10 8 0.20 35Cl or Cl-35 17 18 17 75.53 37Cl or Cl-37 17 20 17 24.47 3.8 Atomic Weight Dalton recognized the hopelessness of ascertaining the absolute weights of atoms because atoms are much too small to be weighted. It is possible to compare the weights of a large number of atoms of element A with that of the same number of atoms of element B. Atomic Weights for elements are determined by comparing a very large number of the atoms of the element with the same number of atoms of C-12. By definition the atomic weight of C-12 is exactly 12. For instance, the atomic weight of H is 1.008, meaning that H atoms are about one-twelfth as heavy as C-12 atoms. Calculating the atomic weight The atomic weight of an element is the weighted average of the atomic weights of all its natural isotopes and can be calculated if the atomic weights and relative abundances of the isotopes are given. E.g., There are two naturally occurring chlorine isotopes, Cl-35 and Cl-37, with relative abundances of 75.5% and 24.5%, respectively. Atomic Weight Cl = (0.755 × 35.0) + (0.245 × 37.0) Atomic Weight Cl = 35.5 3.9 Formula Weight The formula weight of an element or compound is calculated by adding the atomic weights all the atoms in its formula

e.g.FormulaWeightof0,=2×16.0=32.0FormulaweightofH0=2×1.0+1X16.0=18.03.10ElectronsinAtomsItis the electrons thatare responsible forthe chemical properties of atoms.Electrons form thebondsthatconnectatomstooneanothertoformmolecules.Thewayinwhichtheelectronsaredistributed in anatoms is calledtheelectronicstructureoftheatom.Inanatom,thesmall,heavypositivenucleus is surroundedbycirculatingelectrons.3.11ElectronicConfigurationsEach electron in an atom possesses a total energy (kinetic pluspotential).The lowest-energy electrons are those closest to the nucleusoftheatomandthemostdifficulttoremovefromtheatom.NielsBohr(1885-1962), a Danish physicist, first introduced the idea of electronicn: principal auantum numberenergy levelsBohr's Atomic Model was based on the Quantum Theory of Energy. The energy levels in atoms canbepictured as orbits in which electrons travel at definite distancesfrom the nucleus.Thesehe called"quantized energy levels", also known as principal energy levels.Schrodinger'sAtomic TheoryBohr's theory laid the groundwork for modem atomic theory.In 1926, Erwin Schrodinger proposedthe modern picture of the atom, which is based upon a complicated mathematical approach and is usedtoday. In the Schrodinger atom, the principal energy level used by Bohr are further divided intosublevels, which aredesignated(指派）by a principal quantum number and a lowercase letter (s,p, dandJ). The higher the energy level, the more sublevels there are. The electronic levels (Is, 2s,2p and so on)are also called orbitals.1sorbitalPx orbital(and so on)1Pz orbitalPy orbitalIs2s2p3s3p4s3dAtomicOrbitalsShapes of atomic orbitals:s orbital is spherical;p orbitals are dumbbell-shaped.9

9 e.g. Formula Weight of O2 = 2 × 16.0 = 32.0 Formula weight of H2O = 2×1.0 + 1 × 16.0 = 18.0 3.10 Electrons in Atoms It is the electrons that are responsible for the chemical properties of atoms. Electrons form the bonds that connect atoms to one another to form molecules. The way in which the electrons are distributed in an atoms is called the electronic structure of the atom. In an atom, the small, heavy positive nucleus is surrounded by circulating electrons. 3.11 Electronic Configurations Each electron in an atom possesses a total energy (kinetic plus potential). The lowest-energy electrons are those closest to the nucleus of the atom and the most difficult to remove from the atom. Niels Bohr (1885-1962), a Danish physicist, first introduced the idea of electronic energy levels. Bohr’s Atomic Model was based on the Quantum Theory of Energy. The energy levels in atoms can be pictured as orbits in which electrons travel at definite distances from the nucleus. These he called “quantized energy levels”, also known as principal energy levels. Schrödinger’s Atomic Theory Bohr’s theory laid the groundwork for modern atomic theory. In 1926, Erwin Schrödinger proposed the modern picture of the atom, which is based upon a complicated mathematical approach and is used today. In the Schrödinger atom, the principal energy level used by Bohr are further divided into sublevels, which are designated(指派）by a principal quantum number and a lowercase letter ( s, p, d and f). The higher the energy level, the more sublevels there are. The electronic levels (1s, 2s,2p and so on) are also called orbitals. 1s 2s 2p 3s 3p 4s 3d (and so on) y x z y x z y x z y x z s orbital px orbital pz orbital py orbital Atomic Orbitals Shapes of atomic orbitals: s orbital is spherical; p orbitals are dumbbell-shaped. n=1 n=2 n=3 n=4 n: principal quantum number