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.jp
2、gAtomsnMatter 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 ar
3、e three 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 a
4、n atom.nNeutrons 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 clou
5、ds or shells.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+-
6、noneAtomic Structure 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: Car
7、bon = CTwo lettersone capitol, 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
8、 ATOM, YOU CHANGE ITS IDENTITY!1H12Mg82PbAtomic 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 At
9、omic Number, we can figure out the number of neutrons.Pb n(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 prot
10、ons in an elementnAlso, number of electrons when it is neutral (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 S
11、tructure (cont.)nPractice Problem #1nFor a sodium atom:What is the atomic 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
12、number?nHow many protons?nHow many electrons since it is neutral?What 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 fro
13、m metals metalloids nonmetalsThe Periodic TablenOrganized by trends and 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 c
14、onductors of heat and electricitynMOST are solid at room temperatureNonmetalsnGain 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 bot
15、h metals and nonmetalsLess conductive than metals, but poorer insulators than nonmetalsnElectrons 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 - Histor
16、ynWhen Mendeleev arranged them by Atomic Mass, he was able to predict the properties of 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 M
17、oseley reordered the Periodic Table by Atomic NumberGroups and FamiliesnThe columns on the 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
18、reactive!nHydrogen is NOT includedAlkaline Earth MetalsnGroup 2AnTwo valence electronsnNot 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 a
19、lso known as the Rare Earth Metals!HalogensnGroup 7AnSeven valence electronsnVERY reactive!Noble 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 clou
20、d = 83rd cloud = 8These cloud layers conveniently match the rows on the periodic table:1st row = 2 elements2nd 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
21、 first cloudnSulfur has:16 electronsElectron Clouds (cont.)nPractice ProblemDraw the electron clouds for 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 importa
22、nt electronsare called the outer, or valence, electronsJust draw the outer electronsaround the atomic symbolSLewis 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 el
23、ectronicallynThese elements have 8 electrons in highest energy leveln8 is GREATLewis Dot Structures (cont.)nAll 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 ele
24、ctronsCharged atoms are called ions: cations if they are positive and anions if they are negativeAtomic Number 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 Numb
25、er)19-(Charge)1=18 ElectronsnCa?nIf the element has a negative chargeTake the atomic number and Add the charge to 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
26、will it become?1lose1+1IonsnHow many valence electrons in O?nIs it easier to gain or lose to become full?nHow many will it gain or lose?nWhat charge will it become?6gain2-2IonsMagnesium-24+2Sulfur-33-2Phosphorus-34-3NameSymbolAtomic #Mass #ProtonsNeutronsElectronsChargeAtomic TablesnRulesNamenComes
27、from Periodic Table WITH Mass NumberSymbolnComes from Periodic TableAtomic NumbernTop Number, Same as number of ProtonsMass NumbernEqual to Number of Protons + Number of Neutronsn(Usually Bottom Number of Periodic Table Rounded)Atomic Tables ContinuedProtonsnEqual to Atomic Number (Top)Neutronsn= Ma
28、ss 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
