The-Atom-and-the-Periodic-Table原子与元素周期表课件.ppt

1、The Atom and the Periodic TableAtomsnEverything in the Universe is made of stuff(also known as matter).nThe building blocks are the same,whether we are looking at Stars or Starbursts.jakehowlett/tuckshop/wrappers/sweets/fruits/starburst.jpglibrary.thinkquest.org/12659/media/solar_system/sun/sun.jpgA

2、tomsnMatter is made up of Atoms.nAtoms are the smallest particle of an element.nThey are so small that:1 sheet of paper=10,000 atoms thick1 drop of water has 2 trillion atoms of oxygen and 4 trillion atoms of hydrogen.nThe three parts of an atom are:ProtonsNeutronsElectronsAtoms ProtonsnThere are th

3、ree types of particles that make up atomsnThe first type of particle is called the PROTON.nProtons are found in the nucleus of an atom.nProtons have a positive(+)charge.nProtons have a mass of 1 a.m.u.Atoms-NeutronsnAnother particle is the NEUTRON.nNeutrons are also found in the nucleus of an atom.n

4、Neutrons have no charge.We call this neutral.nNeutrons have a mass of 1 a.m.u.nNeutrons act like the glue that holds the nucleus together.Atoms-ElectronsnElectrons are the third type of particle inside of an atom.nThey are very small,and exist outside of the nucleus in the electrons clouds or shells

5、.nElectrons have a negative charge(-)and have almost no mass at all.Atomic StructurenAtoms are made up of three subatomic particles:Subatomic=smaller than an atomLive where?Have mass?What charge?ProtonsNeutronsElectronsIn nucleusIn nucleusOutside nucleus1 a.m.u1 a.m.uNo,negligible+-noneAtomic Struct

6、ure VideoElementsnSubstances made of only one type of atomnIdentified by atomic number(protons!)nCan not be broken down into simpler substancesElement SymbolsnShorthand name of the elementnMost are based on the Latin nameEx:Gold=AunThe symbol is either:One capital letter-ex:Carbon=CTwo lettersone ca

7、pitol,one lower case-ex:Krypton=KrAtomic NumbernTop Number indicates Atomic NumbernAtomic Number=Number of ProtonsHydrogen:nAtomic Number 1=1 protonMagnesium:nAtomic Number 12=12 protonsLead:nAtomic Number 82=82 ProtonsnIF YOU CHANGE THE NUMBER OF PROTONS OF AN ATOM,YOU CHANGE ITS IDENTITY!1H12Mg82P

8、bAtomic MassnBottom Number indicates Atomic MassnAtomic Mass=Total Mass(Number of Protons+Number of Neutrons)Hydrogen:n1(Protons+Neutrons)Magnesium:n24(Protons+Neutrons)Lead:n207(Protons+Neutrons)nIf we take the Atomic Mass and subtract the Atomic Number,we can figure out the number of neutrons.Pb n

9、(Atomic Mass)n207 n n(Atomic Number)n82n=n125H1Mg24Pb207Atomic Structure(cont.)nAtomic MassnAverage mass of an element,based on amount of each isotope found in naturenNot a whole number because it is an averagenAtomic numbernNumber of protons in an elementnAlso,number of electrons when it is neutral

10、(has no charge)7N14.011Atomic Structure(cont.)nFor a lithium(Li)atom:What is the atomic number?nHow many protons?nHow many electrons since it is neutral?What is the atomic mass?nHow many neutrons?3336.939 rounded to 7Usually 4Atomic Structure(cont.)nPractice Problem#1nFor a sodium atom:What is the a

11、tomic number?nHow many protons?nHow many electrons since it is neutral?What is the atomic weight?nHow many neutrons?11111122.99 rounded to 23Usually 12Atomic Structure(cont.)nPractice Problem#2nFor a boron atom:What is the atomic number?nHow many protons?nHow many electrons since it is neutral?What

12、is the atomic weight?nHow many neutrons?55510.811 rounded to 11Often 6PeriodsnThe elements are arranged on the periodic table of elementsnGoing horizontal across the table are the PERIODSnStarting from the left,the periods go from metals metalloids nonmetalsThe Periodic TablenOrganized by trends and

13、 patterns“periodic”means repeatingnThis allows you to make predictions about the atoms behavior based on where they are on the tableMetalsnLose electrons to form positive ionsnDuctile&MalleableWhat do these words mean?nGood conductors of heat and electricitynMOST are solid at room temperatureNonmeta

14、lsnGain electrons to form negative ionsnBrittlenGood insulatorsnFound as solid,liquid,or gas at room tempMetalloids(semi-metals)nFound directly on either side of side-step lineExcept Al(this is a metal!)nProperties of both metals and nonmetalsLess conductive than metals,but poorer insulators than no

15、nmetalsnElectrons held more tightly than metals,but can be freed with heatPeriodic Table-HistoryDimitry Mendeleev was a Russian(actually Siberian)scientist that lived in the late 19th Century.Periodic Table-HistorynWhen Mendeleev arranged them by Atomic Mass,he was able to predict the properties of

16、elements that had not yet been discovered.nThis is the basis of the Periodic Table that we use today.Periodic Table-HistoryNow the Periodic Table that we use is arranged by Atomic Number instead of Mass.Henry Moseley reordered the Periodic Table by Atomic NumberGroups and FamiliesnThe columns on the

17、 periodic table are called groups and families.nThe groups are the numbers;the families are the namesnThey are organized by the number of valence electronsAlkali MetalsnGroup 1AnOnly one valence electronnVERY reactive!nHydrogen is NOT includedAlkaline Earth MetalsnGroup 2AnTwo valence electronsnNot

18、as reactive as the alkali metalsnNamed because of where they are found on EarthTransition MetalsnFound in the middle of the tablenIn the“B Groups”nCan change their number of valence electronsBottom Rows are also known as the Rare Earth Metals!HalogensnGroup 7AnSeven valence electronsnVERY reactive!N

19、oble GasesnGroup 8An8 valence electronsouter energy level is fullnVery UNREACTIVEwhat do they need to be Electron CloudsnThe different layers of clouds hold different numbers of electrons1st cloud=22nd cloud=83rd cloud=8These cloud layers conveniently match the rows on the periodic table:1st row=2 e

20、lements2nd row=8 elements3rd row=8 elementsAnd then it gets complicatedElectron Clouds(cont.)nTo draw the electron clouds:Figure out how many total electronsFill in the electrons starting with the first cloudnSulfur has:16 electronsElectron Clouds(cont.)nPractice ProblemDraw the electron clouds for

21、an Al atomThis is WAY too much workthere must be a simpler way!Lewis Dot StructuresnA smart man named Gilbert Newton Lewis figured out an easier way!For Lewis Dot Structures draw only the important electronsare called the outer,or valence,electronsJust draw the outer electronsaround the atomic symbo

22、lSLewis Dot Structures(cont.)nPractice Problem#4Draw Lewis Dot Structures for:A Calcium atomA Chlorine atomAn Oxygen atomCaOClOctet RulenNoble gases are what all elements aspire to be like electronicallynThese elements have 8 electrons in highest energy leveln8 is GREATLewis Dot Structures(cont.)nAl

23、l elements want to be full of electrons:So they gain or lose electrons until they are fullThis gives the atom a chargenNegative charge if they gain electronsnPositive charge if they lose electronsCharged atoms are called ions:cations if they are positive and anions if they are negativeAtomic Number

24、ContinuednAlso equal to number of electrons if the atom has no chargenIf the Element has a positive chargeTake the atomic number and Subtract the charge to find#of electronsnK(Atomic Number)19-(Charge)1=18 ElectronsnCa?nIf the element has a negative chargeTake the atomic number and Add the charge to

25、 find the number of electronsnCl17+1=18 Electrons+1K+2Ca-1ClIonsnHow many valence electrons in Li?nIs it easier to gain or lose to become full?nHow many will it gain or lose?nWhat charge will it become?1lose1+1IonsnHow many valence electrons in O?nIs it easier to gain or lose to become full?nHow man

26、y will it gain or lose?nWhat charge will it become?6gain2-2IonsMagnesium-24+2Sulfur-33-2Phosphorus-34-3NameSymbolAtomic#Mass#ProtonsNeutronsElectronsChargeAtomic TablesnRulesNamenComes from Periodic Table WITH Mass NumberSymbolnComes from Periodic TableAtomic NumbernTop Number,Same as number of Prot

27、onsMass NumbernEqual to Number of Protons+Number of Neutronsn(Usually Bottom Number of Periodic Table Rounded)Atomic Tables ContinuedProtonsnEqual to Atomic Number(Top)Neutronsn=Mass Number Number of ProtonsElectronsnIf No ChargeEqual to Number of ProtonsnIf Has a Positive ChargeSubtract Charge from Number of ProtonsnIf Has a Negative ChargeAdd Charge to Number of ProtonsPractice ProblemsNameSymbolAtomic NumberMass NumberProtonsNeutronsElectronsCharge10030260Na23+11616-2Nitrogen-1510Neon-20Ne122656261020101018FeIron-56Sodium-23111110Sulfur-32S32167N1578-3