2Basic Vocabulary Matter: Anything that has mass and volume Mass: Amount of matter in an objectWeight: Measure of the force of attraction between objects due to mass and gravityVolume: Amount of space an object takes upDensity: Measurement of how much mass is contained in a given volume
3More VocabularyAtoms: Smallest particle of an element that has all the properties of matter:Protons- particles in the nucleus with positive chargeElectrons- particles orbiting around nucleus with negative chargeNeutrons- particles in the nucleus with no chargeElements: Simplest form of a pure substanceCompounds: Two or more elements chemically combined to form a new substance
4Sub-Atomic Particles Part of Atom Charge Location Mass/Size Electron - negativeoutside nucleus.0006 amu(too little to count)Proton+ positiveinside nucleus1 amuNeutronno charge
6Using the Periodic Table Atomic NumberEqual to # protons = # electronsPeriodic Table is arranged by this numberSymbol“Shorthand” for the element – Note 2nd letter is always lowercaseAtomic Mass NumberTotal AVERAGE mass of Protons + Neutrons + Electrons17Cl35.5
7Electron Energy Levels Electrons are arranged in “Shells” around nucleus in predictable locationsFill “seats” closest to nucleus first (concert – best seats)“Seats” availableShell #1 2 electronsShell #2 8 electronsShell #3 8 electronsShell # electronsShell # electronsShell #6 50 electronsEx. Carbon has 6 total electrons so…Two electrons on first energy levelFour electrons on second energy levelQuestion: Could we fit more electrons on the second energy level if there were more electrons in carbon??
8Atomic StructureTotal # of protons and electrons (in a neutral atom)17 protons in nucleus17 electrons orbiting nucleus17ClElement NameChlorine35.5Total Mass of Nucleus= 18 neutrons(Round Atomic Mass)Notice: electrons follow energy level rulesfrom previous slide.
9Atomic Mass – Fractions? Look at Chlorine (atomic number 17)Atomic mass of 35.5? I dont’ get it!Where does the 35.5 come from?0.5 protons? 0.5 neutrons? NoAtomic Mass = average number of protons and neutrons in nature
10More PracticeDetermine the name, number of protons, neutrons and electrons for each element shown and draw…26815FeOP561631
11IsotopesAn isotope is a variation of an element (same protons) but can have diff. # of neutronsEx: carbon (atomic mass = )Carbon (14) and carbon (12) exist in nature
12Ions Change in electrons which gives an atom a charge (+ or -) You can only add or subtract electrons! (protons don’t change)Ex. Count the number of electrons below…Carbon ion (-1 charge)7 electrons (-)6 protons (+)Neutral Carbon6 electrons (-)6 protons (+)Carbon ion (+1 charge)5 electrons (-)6 protons (+)
13Valence Electrons An electron on the outermost energy shell of an atom Important to understand because this is a key factor in how atoms will BOND with each otherOctet rule – stable atom will have 8 electrons in that outer shellPractice – Valence # ofChlorine?Neon?Nitrogen?Oxygen?
14Electron Dot Diagramsa diagram that represents the # of valence electrons in an atom of an element.The amount of electrons is displayed by dots around the symbol of the element.Ex.o/sho/lessons/lesson38.htm
15Types of Chemical Bonds Ionic- Two elements bond by transferring electrons to create ionsthat attract together (+ is attracted to - after an electron istransferred)Covalent- Two elements bond by sharing electrons(strongest bond type)Metallic- Two metals bond and form a “common electron cloud”.This is a cluster of shared electrons (weakest bond type)
16Examples of Bonding http://www.youtube.com/watch?v=xTx_DWboEVs
17Predicting Bonds Ionic Bond = metal to non-metal Covalent = non-metal to non-metalMetallic = metal to metalDo you understand why? HINT: the numbers at the top of the table indicate the # of valence electrons for each column
18Oxidation Numbers Oxidation numbers are assigned to each element They represent a predicted “charge” of an atom/ion when it bonds with another element.(tells us if the atom would prefer give or take electrons, and how many).They help us to predict what compounds will form when two elements get together.Oxidation numbers are labeled like this:Na 1+O 2-
19How to Use Oxidation Numbers Oxidation Number indicates the number of electrons lost, gained or shared when bonding with other atoms.Ex. Na wants to lose an electron. If an electron is lost, it becomes a +1 chargeSO: oxidation number for Na = 1+Ex. Cl wants to gain an electron. If an electron is gained, it becomes a -1 chargeSO: oxidation number for Cl = 1-
20Oxidation NumbersEach column going down the periodic table has elements with the same oxidation number.
21The oxidation numbers are at the top of each column as shown here: (+/-)
22Rules for using oxidation numbers to create compounds Positive ions can only bond with negative ions and vice versa2. The sum of the oxidation numbers of the atoms in a compound must be zero (the key is to stay balanced)3. If the oxidation numbers are not equal to zero, then you must add additional elements until they balance at zero.4. When writing a formula the symbol of the Positive (+) element is followed by the symbol of the negative (-) element.
23Examples of Forming Compounds Ex. Na (+1) + Cl (-1) = NaClAre these oxidation numbers already equal to zero?If so, you don’t need to add any extra elements to combine them into a compound, so the answer is simply NaClEx. H (+1) + O (-2) = H2OHow many +1 would you need to balance the -2 to zero?Since you need 2 atoms of the 1+ to balance the 2- to zero the resulting compound would be H2OIn other words: to combine H with O, you MUST have 2 H to balance the oxidation numbers to zero2+ and = ZEROEx. Al (+3) + S (-2) = Al2S3This one is tricky…we are not even close to balancing + and - to zero.Because of this we must have more than one Al and more than one S in our final equation.By using 2 Aluminums instead of just1 we would have 6+By using 3 sulfers instead of just 1 we would have 6-Since these are now equal to zero, we combine 2 Aluminums and 3 Sulfers to make Al2S3
24Chemical vs. Physical Change Physical Change: A change that can occur without changing the identity of the substance.Ex. Solid, Liquid, Gas (Phase change)PlasmaChemical Change: Process by which a substance becomes a new and different substanceEx. Fire
25Chemical ReactionsChemical Reaction: a process in which the physical and chemical properties of the original substance change as new substances with different physical and chemical properties are formed
26Chemical Reaction Basics H2 + O2 --> H2OReactantsProductsReactants- substance that enters into a reactionProducts- substance that is produced by a chemical reaction
27Evidence of Chemical Change EPOCH is an acronym that stands for evidencethat a chemical reaction has occurred.– Effervescence (bubbles and/or gives off gas)– Precipitate (solid crystals form)– Odor (change of smell is detected)– Color change– Heat (reaction either heats up or cools down)Does sighting evidence of a chemical reaction mean that a chemical reaction has undoubtedly taken place?EPOCH
28Types of Reactions Romance Chemistry :) Synthesis- Marriage/DatingA + B = ABDecomposition- Divorce/BreakupAB= A + BSingle-Replacement- Dance Cut InA + BC = AC + BDouble-Replacement- Dancing couples switch partners.AB + CD = AC + BD
29Cartoon ChemistryThis is an example of synthesis
30Cartoon ChemistryThis is an example of a decomposition
31Cartoon ChemistryThis is an example of a single replacement
32Cartoon ChemistryThis is an example of a double replacement
33Reaction Types Review… Match each chemical reaction with one of the reaction types on your chemical cartoons.Zn + 2HCl H2 + ZnCl2N2 + 3H2 2NH32KI + Pb(NO3)2 2KNO3 + PbI22MgCl Mg2 + Cl2
34Conservation of MassAtoms cannot be created or destroyed in a chemical reaction.What goes in must come out.So we must balance equations to conserve mass.
35Balancing Equations Rules: Ex. 2H2 + O2 --> 2H2O We can not add or subtract subscripts from either side of the equationWe can only add coefficients to the front of each compoundEx H O2 --> 2H2OH = H = 4O= O = 2Before must match AfterSee “Balancing Act” worksheet for more examples…
36Solution ChemistryMixtures: Matter that consists of two or more substances mixed but not chemically combinedSolutions: Homogeneous Mixture in which one substance is dissolved into anotherSolute = Substance that gets dissolved (ex. Kool-Aid powder)Solvent = Substance that does the dissolving (ex. Water)Acid: Compound with a pH below 7 that tastes sour and is a proton donor.Ex. Citrus foodsBase: Compound with a pH above 7 that tastes bitter and is a proton acceptorEx. Cleaning Products (soap)
37Acids and Bases Solutions can be acidic or basic Acids and Bases have unique properties when dissolved in waterAcids = sour tasteBases = bitter tasteIndicators are substances that change color when mixed with a solution, which helps to determine if a substance is an acid or a base. (pH paper, Litmus paper, cabbage juice)
38Acids Proton donors (H+) Acids contain hydrogen and produce positive ions (H+) when dissolved in waterAcids = good electrolytesExamples of acids:Lemon JuiceCitric AcidCarbonic AcidHCl
39Bases Proton acceptors Bases contain hydroxide ions (OH-) when mixed with water.Bases = weak electrolytesExamples of bases:AmmoniaSoapBleach (chlorine)
40Combining Acids and Bases -Mixing acids and bases is a balancing act.(like a teeter-totter)Acid + Base = neutral (water and salt)
41Combining Acids and Bases EXAMPLE:Acid + Base = neutral (water and salt)H OH- HOH SaltAcid Base waterEx. HCl NaOH H2O + NaCl
42Measuring Acids and Bases pH scale- used to measure the acidity of a solution.Measure pH with indicatorspH scale goes from 0 – 140 = very acidic14 = very basic7 = neutral