TheAtomandthePeriodicTable原子与元素周期表课件.ppt

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

2、g,Atoms,Matter is made up of Atoms.Atoms are the smallest particle of an element.They 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.The three parts of an atom are:ProtonsNeutronsElectrons,Atoms Protons,There are t

3、hree types of particles that make up atomsThe first type of particle is called the PROTON.Protons are found in the nucleus of an atom.Protons have a positive(+)charge.Protons have a mass of 1 a.m.u.,Atoms-Neutrons,Another particle is the NEUTRON.Neutrons are also found in the nucleus of an atom.Neut

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

5、rons have a negative charge(-)and have almost no mass at all.,Atomic Structure,Atoms are made up of three subatomic particles:,Subatomic=smaller than an atom,In nucleus,In nucleus,Outside nucleus,1 a.m.u,1 a.m.u,No,negligible,+,-,none,Atomic Structure Video,Elements,Substances made of only one type

6、of atomIdentified by atomic number(protons!)Can not be broken down into simpler substances,Element Symbols,Shorthand name of the elementMost are based on the Latin nameEx:Gold=AuThe symbol is either:One capital letter-ex:Carbon=CTwo lettersone capitol,one lower case-ex:Krypton=Kr,Atomic Number,Top N

7、umber indicates Atomic NumberAtomic Number=Number of ProtonsHydrogen:Atomic Number 1=1 protonMagnesium:Atomic Number 12=12 protonsLead:Atomic Number 82=82 ProtonsIF YOU CHANGE THE NUMBER OF PROTONS OF AN ATOM,YOU CHANGE ITS IDENTITY!,1H,12Mg,82Pb,Atomic Mass,Bottom Number indicates Atomic MassAtomic

8、 Mass=Total Mass(Number of Protons+Number of Neutrons)Hydrogen:1(Protons+Neutrons)Magnesium:24(Protons+Neutrons)Lead:207(Protons+Neutrons)If we take the Atomic Mass and subtract the Atomic Number,we can figure out the number of neutrons.Pb(Atomic Mass)207(Atomic Number)82=125,H1,Mg24,Pb207,Atomic St

9、ructure(cont.),Atomic MassAverage mass of an element,based on amount of each isotope found in natureNot a whole number because it is an averageAtomic numberNumber of protons in an elementAlso,number of electrons when it is neutral(has no charge),Atomic Structure(cont.),For a lithium(Li)atom:What is

10、the atomic number?,How many protons?,How many electrons since it is neutral?,What is the atomic mass?,How many neutrons?,3,3,3,6.939 rounded to 7,Usually 4,Atomic Structure(cont.),Practice Problem#1For a sodium atom:What is the atomic number?How many protons?How many electrons since it is neutral?Wh

11、at is the atomic weight?How many neutrons?,11,11,11,22.99 rounded to 23,Usually 12,Atomic Structure(cont.),Practice Problem#2For a boron atom:What is the atomic number?How many protons?How many electrons since it is neutral?What is the atomic weight?How many neutrons?,5,5,5,10.811 rounded to 11,Ofte

12、n 6,Periods,The elements are arranged on the periodic table of elementsGoing horizontal across the table are the PERIODSStarting from the left,the periods go from metals metalloids nonmetals,The Periodic Table,Organized by trends and patterns“periodic”means repeatingThis allows you to make predictio

13、ns about the atoms behavior based on where they are on the table,Metals,Lose electrons to form positive ionsDuctile&MalleableWhat do these words mean?Good conductors of heat and electricityMOST are solid at room temperature,Nonmetals,Gain electrons to form negative ionsBrittleGood insulatorsFound as

14、 solid,liquid,or gas at room temp,Metalloids(semi-metals),Found directly on either side of side-step lineExcept Al(this is a metal!)Properties of both metals and nonmetalsLess conductive than metals,but poorer insulators than nonmetalsElectrons held more tightly than metals,but can be freed with hea

15、t,Periodic Table-History,Dimitry Mendeleev was a Russian(actually Siberian)scientist that lived in the late 19th Century.,Periodic Table-History,When Mendeleev arranged them by Atomic Mass,he was able to predict the properties of elements that had not yet been discovered.This is the basis of the Per

16、iodic Table that we use today.,Periodic Table-History,Now the Periodic Table that we use is arranged by Atomic Number instead of Mass.,Henry Moseley reordered the Periodic Table by Atomic Number,Groups and Families,The columns on the periodic table are called groups and families.The groups are the n

17、umbers;the families are the namesThey are organized by the number of valence electrons,Alkali Metals,Group 1AOnly one valence electronVERY reactive!Hydrogen is NOT included,Alkaline Earth Metals,Group 2ATwo valence electronsNot as reactive as the alkali metalsNamed because of where they are found on

18、 Earth,Transition Metals,Found in the middle of the tableIn the“B Groups”Can change their number of valence electrons,Bottom Rows are also known as the Rare Earth Metals!,Halogens,Group 7ASeven valence electronsVERY reactive!,Noble Gases,Group 8A8 valence electronsouter energy level is fullVery UNRE

19、ACTIVEwhat do they need to be,Electron Clouds,The different layers of clouds hold different numbers of electrons1st cloud=22nd cloud=83rd cloud=8,These cloud layers conveniently match the rows on the periodic table:1st row=2 elements2nd row=8 elements3rd row=8 elementsAnd then it gets complicated,El

20、ectron Clouds(cont.),To draw the electron clouds:Figure out how many total electronsFill in the electrons starting with the first cloudSulfur has:16 electrons,Electron Clouds(cont.),Practice ProblemDraw the electron clouds for an Al atom,This is WAY too much workthere must be a simpler way!,Lewis Do

21、t Structures,A 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,electrons,Just draw the outer electronsaround the atomic symbol,S,Lewis Dot Structures(cont.),Practice Problem#4Draw Lewis Dot Struc

22、tures for:A Calcium atomA Chlorine atomAn Oxygen atom,Octet Rule,Noble gases are what all elements aspire to be like electronicallyThese elements have 8 electrons in highest energy level8 is GREAT,Lewis Dot Structures(cont.),All elements want to be full of electrons:So they gain or lose electrons un

23、til they are fullThis gives the atom a chargeNegative charge if they gain electronsPositive charge if they lose electrons,Charged atoms are called ions:cations if they are positive and anions if they are negative,Atomic Number Continued,Also equal to number of electrons if the atom has no chargeIf t

24、he Element has a positive chargeTake the atomic number and Subtract the charge to find#of electronsK(Atomic Number)19-(Charge)1=18 ElectronsCa?If the element has a negative chargeTake the atomic number and Add the charge to find the number of electronsCl17+1=18 Electrons,+1K,+2Ca,-1Cl,Ions,How many

25、valence electrons in Li?Is it easier to gain or lose to become full?How many will it gain or lose?What charge will it become?,1,lose,1,+1,Ions,How many valence electrons in O?Is it easier to gain or lose to become full?How many will it gain or lose?What charge will it become?,6,gain,2,-2,Ions,Atomic

26、 Tables,RulesNameComes from Periodic Table WITH Mass NumberSymbolComes from Periodic TableAtomic NumberTop Number,Same as number of ProtonsMass NumberEqual to Number of Protons+Number of Neutrons(Usually Bottom Number of Periodic Table Rounded),Atomic Tables Continued,ProtonsEqual to Atomic Number(T

27、op)Neutrons=Mass Number Number of ProtonsElectronsIf No ChargeEqual to Number of ProtonsIf Has a Positive ChargeSubtract Charge from Number of ProtonsIf Has a Negative ChargeAdd Charge to Number of Protons,Practice Problems,Neon-20,Ne,12,26,56,26,10,20,10,10,18,Fe,Iron-56,Sodium-23,11,11,10,Sulfur-32,S,32,16,7,N,15,7,8,-3,