Lecture 3 Outline of Last Lecture I. Elements ContinuedII. The Periodic TableIII. Atoms & MoleculesIV. Diatomic MoleculesV. Formulas & NamesVI. Chemical ReactionsOutline of Current Lecture I. Characteristics of Chemical EquationsII. Balancing EquationsIII. Balancing Equations ExamplesIV. Ozone: What is it?V. Atomic Structure & PeriodicityCurrent LectureI. Characteristics of Chemical Equationsa. Can’t create or destroy atoms. Can’t change an atom into another kind of atom (chemically). b. H2 + O2  H2Oc. Hydrogen reacts with oxygen to make water.d. This equation is implying an oxygen atom has been destroyed so therefore we need to balance it. 2H2 + O2  2H20e. Mg + O2  MgO (combustion reaction)f. 2Mg + O2  2MgO g. The number in front of the element they are talking about is called a coefficient. The number behind the element is called a subscript.h. It’s okay to use trial and error when balancing equations.II. Balancing Equationsa. ID Reactants & Productsb. The reactants in the equation is on the lefc. The products in the equation is on the rightd. Change the coefficient to make the number of atoms on each side equal.e. DO NOT CHANGE SUBSCRIPTS. You cannot just add subscripts wherever you want because you are creating compounds that do not exist.f. You can only add coefficientsg. Start with atoms that appear once on each side. Chem 1100h. Double-check and make sure everything is equal and that you haven’t created or destroyed anything.i. KClO3  O2 + KCl (decomposition reaction)j. K & Cl are already balanced^^k. The lowest common multiple of 2 and 3 is 6. l. Balanced: 2KClO3  3O2 + 2KClIII. Balancing Equations Examplesa. C + O2  CO BALANCED = 2C + O2  2COb. H2 + Br2  HBr BALANCED = H2 + Br2  2HBrc. K + H2O  KOH + H2 BALANCED = 2K + 2H2O  2KOH + H2d. Zn + AgCl  ZnCl2 + Ag BALANCED Zn + 2AgCl  ZnCl2 + 2Age. NaOH + H2SO4  Na2SO4 + H2O BALANCED 2NaOH + H2SO4  Na2SO4 + 2H2Of. KOH + H3PO4  K3PO4 + H2O BALANCED 3KOH + H3PO4  K3PO4 + 3H2OIV. Ozone: What is it?a. O3 – ozone (element)i. Elemental oxygen – different from regular oxygen. Three oxygen atoms bonded together. b. Allotropes: Same element, different arrangement (diamond vs. graphite)i. If you get anything cold enough you can liquefy it.c. Oxygen vs. Ozonei. Oxygen: colorless gas, odorless, light blue liquid, boiling point: -193 C, reactive.ii. Ozone: colorless gas, definite odor (metallic/tangy), dark blue liquid, boiling point: -112 C, more reactive than oxygen.d. Where is Ozone?i. High up in the stratosphere. We are in the troposphere. The troposphere is between 0 – 9.3 miles of altitude. The stratosphere is between 9.3 – 21.7 miles of altitude. e. Good & Bad Ozonei. Upper atmosphere: The ozone blocks UV rays which is a good thing for us. It protects us from it. It helps prevent sunburn and cancer.1. 90% of O3  “ozone layer”2. Altitude: 9.3-18.6 milesii. Lower Atmosphere: photochemical smog (as in L.A)  bad1. 10% of O32. 1.5 miles and loweriii. How does O3 have its effects?V. Atomic Structure & Periodicitya. Atoms: have two regions (nucleus & the outer part where the electrons orbit)b. Nucleus – very dense center of the atom. The vast majority of mass lies within in the nucleus. It contains the protons and neutrons.c. Orbit Nucleus – the electrons orbit the nucleus.d. Electrons are negatively charged, they orbit the nucleus, and they are very tiny compared to protons.e. Protons are positively charged, exist in the nucleus, they are 2000 times the size of an electron.f. Neutrons have no charge, they are found in the nucleus, and they are also 2000 times the size of an electron. g. A neutral atom has no charge. It means the number of protons in the nucleus equal the number of electrons orbiting the nucleus.h. What determines the kind of atom you have is the number of protons in the nucleus. Ex: carbon has 6 protons in its nucleus. If it doesn’t, its not carbon.i. Proton +1 charge. Neutron 0 charge. Electron -1 charge.j. Proton relative mass 1. Neutron relative mass 1. Electron relative mass 0.i. An electrons relative mass in not actually zero but it is so small that it appears as zero when expressed to the nearest whole number.k. Proton actual mass, kg = 1.67 x 10 ^ -27. Neutron actual mass is the same as a protons. Electron actual mass 9.11 x 10 ^ -31.l. The same ELEMENT can have different number of electrons: ionsm. Ions: atoms that have a different number of protons and electrons (they have a charge)n. Examples: when Na loses an electron it becomes positive Na+ ; Fluorine tends to gain electrons so it starts off as F but then can become