AP双语教程-元素周期表.ppt

The important discoveries about the atomDaltons Atomic Theory1.All matter is composed of tiny,indivisible particles,called atoms,that can not be created nor destroyed.2.Each element has atoms that are identical to each other in all of their properties,and these properties are different from the properties of all other atoms.3.Chemical reactions are simple rearrangements of atoms from one combination to another in small whole number ratios.4.He proposed the law of multiple proportions。Thomsons Atomic Theory1.He determined that cathode rays were a fundamental part of matter he called electrons.2He determined their charge to mass ratio by measuring the deflection of the cathode rays in the presence of electric and magnetic fields.3.He proposed the plum pudding model.Rutherfords Atomic Theory1.He performed the gold foil experiment(金箔金箔实验).-particle scattering experiment(粒子散射粒子散射实验)2.He deduced the nuclear model of the atom,with an extremely small,dense,and positively charged nucleus surrounded by empty space sparsely occupied by electrons.Bohrs Atomic TheoryHe assumed that electrons move around the nucleus in circular orbits.He used a solar system model to explain the theory.His most important contribution was the concept that electrons exist in only certain“allowed orbits”.He applied the equations for waves to the electrons in an atom and began the wave-mechanical theory of the atom.The results are very similar to Bohrs model except that the electrons does not follow a precise orbit.Schrodingers Atomic TheorySTRUCTURE of the ATOMn：principal energy levels能能层l：Sublevels(sub shells)能能级m：Orbitals轨道道ms：spin state自旋状自旋状态the principal quantum number主量子数主量子数the azimuthal quantum number角量子数角量子数the magnetic quantum number磁量子数磁量子数the spin quantum number自旋量子数自旋量子数The Periodic TableChemists repeatedly refer to the periodic table to find specific information about the elements and to understand how the properties of the various elements are related to each other.In the table we find chemical and physical similarities between elements in the same group.We also find trends where these properties vary regularly.Atomic symbolsatomic symbolatomic numbermass numberchargesubscriptvalenceatomic symbolatomic numbermass numberchargesubscriptvalenceProtons:number of protons=ZElectrons:number of electrons=Znumber of electrons=Z+/-charge of the ionNeutrons:number of neutrons=A-ZIsotopesA given element have a certain number of protons and electrons.However,it can have varying number of neutrons.Atoms with the same number of protons but different number of neutrons are known as isotopes.Atomic massesThe atomic masses listed in the periodic table are based on defining the atomic mass of pure C-12 as exactly 12.All other masses are relative to that definition.Since most elements have two or more isotopes,the masses listed in the periodic table are the weighted averages of the masses of the naturally occurring isotopes.The modern periodic table1.periodEach row of the periodic table is called period and may contain from 2 to 32 elements.There are seven periods in the periodic table numbered with consecutive whole numbers.1.period the principal energy levelsPeriod 1n=1 Period 2 n=2Period 3n=3Period 4n=4Period 5n=5Period 6n=6Period 7n=7The modern periodic table2.groupEach column is called a group,and elements within groups have similar chemical and physical properties.Within a group,the closer elements are to each other,the more similar they are.There are 16 groups in the periodic table.2.groupGroup AGroup BGroup Group 0Periodic properties of the elementsAlkali metals碱金属碱金属Alkaline earth metals 碱土金属碱土金属Transition elements过渡元素渡元素/过渡金属元素渡金属元素Halogens卤族族Noble gases稀有气体稀有气体/惰性气体惰性气体Lanthanide镧系元素系元素Actinide锕系元素系元素 Metals and metalloidsMetals dominate the elements in the periodic table.Most periodic table show a heavy line diving the metals from the nonmetals.Elements bordering this line are often termed of metalloids since they exhibit some properties of metals and some properties.AllotropesSometimes we encounter an element that has two or more distinct sets of chemical and physical properties.For example:1.Oxygen and ozone are allotropes of oxygen.2.Graphite,diamond,and buckminsterfullerene are three allotropes of carbon.Variation of physical propertiesAs mentioned earlier,the metallic character of the elements increases from the top to the bottom of a group.Many other properties also vary regularly.The melting and boiling points of metals tend to decrease from the top to the bottom of a group.Variation of physical propertiesNonmetals,on the other hand,show an increase in their melting and boiling points.Similar trends in electrical properties,densities,and specific heats are also noted within each group.Atomic radii1.The atomic radius increase from the top to the bottom of a group or family because each increase in period number involves another,larger,energy level.2.When moving from left to right across a period in the periodic table,there is a general decrease in atomic radius because of an increase in the effective nuclear charge.Effective nuclear chargeIonization energyElectron affinityElectro negativityIonic radii