CHEM 101 1st Edition Lecture 3 Outline of Last Lecture I. Kinetic and Potential EnergyII. Units of MeasurementIII. Dimensional AnalysisIV. Performing MeasurementsV. Scientific/Exponential NotationVI.Significant FiguresVII. Start of Chapter 2: The AtomOutline of Current Lecture I. IsotopesII. The Periodic Table of ElementsIII. The Periodic Table of Element GroupsCurrent Lecture- Isotopes- atoms with the same atomic number but different number of neutrons (and therefore different mass numbers)o What else does “12” of C-12 mean?o http:www.nndc.bnl.gov/isotopes/ Aluminum and Phosphate only have 1 isotope each Stable Isotope- may or may not be radioactive, but if radioactive, have half lives too long to be measuredo Hydrogen has 3 isotopes: 11H – 1 proton and 0 neutrons, protiumThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Az CElement SymbolMass number (total number of protons and neutrons in nucleusAtomic number (number of protons in the nucleus) 21H – 1 proton and 1 neutrons, deuterium (D2O; has a higher density than solid water) 31H – 1 proton and 2 neutrons, tritiumo Isotope Electrons Protons Neutrons3216S 16 16 167435Br 35 35 39o The mass spectrometer gives information on the mass and relative (natural) abundance of each element’s isotopeso The % (natural) abundance of each element’s isotopes are found by:% (natural) abundance = number of atoms of an individual isotope x 100of individual isotope total number of atoms of all isotopes of that element Ex: 10 Br: 19.91%11 Br: 80.09%Consider 10,000 B atoms of an average natural sample.% natural abundance of = 19.91% = x x 100 10 10,000 B 11 x = 1991 atoms number of B atoms = 8009 atoms o Clicker Question: Ag has 2 isotopes, one with 60 neutrons (% abundance= 51.839%) and the other with 62 neutrons. What is the symbol of the isotope with62 neutrons, and what is its % abundance? 10947 Ag, 48.161% The Atomic masses on the periodic table are “weighted averages” of all individual isotope masses of an element:Atomic mass = %abundance of isotope 1 x mass isotope 1 100 + %abundance of isotope 2 x mass isotope 2 100 Ex: What is the (average) atomic mass of chlorine? Cl-35 35 17Cl75.77% 34.96885u Cl-37 37 17Cl24.23% 36.96590um(Cl) = m(Cl-35) x abundance of Cl-35 + m(Cl-37) x abundance of Cl-37= (34.96885u x 0.7577) + (36.96590u x 0.2423)= 35.45273522 = 35.45u (4 sig figs) Ex: Co has 2 stable isotopes, Cu-63 and Cu-65. If the masses are 62.9295975u and 64.9277895u respectively, what are the % abundances of the 2 isotopes? The weighted average atomic mass is reported as 63.546uFractional abundance of Cu-63 = x Fractional abundance of Cu-65 = y so 1-x (because x+y =1 and it will be easier to find out while keeping all equations in terms of y=__)m(Cu)=m(Cu-63) times x + m(Cu-65) times y63.549= 64.9277895 + 64.9277895 – 64.9277895x 63.549= 64.9277895 – 1.998192x 1.3787895 = 1.998192x.690018526 so 69.0019% of Cu-63 and 30.99% of Cu-65 - The Periodic Table of Elementsooo Group- the vertical columns in the periodic table. There are 18 groupso Periods- the horizontal rows in the periodic table. There are 7 periods.o Metals Shiny Solids at room temperature (except mercury) High melting points High densities Large atomic radii Low ionization energies Low electro-negativities Usually, high deformation Malleable Ductile Thermal conductors Electrical conductorso Metalloids Electro-negativities between those of metals and nonmetals Ionization energies between those of metals and nonmetals Posses some characteristics of metals/some of nonmetals Reactivity depends on properties of other elements in reaction Good semi-conductorso Nonmetals High ionization energies High electro-negativities Poor thermal conductors Poor electrical conductors Brittle solids Little or no metallic luster Gain electrons easilyo Transition Metals Low ionization energies Positive oxidation states Very hard High melting points and boiling points High electrical conductivity Malleable- Group 1Ao Elements of the first main group are known as Alkali metals (Li, Na, K, Rb, Cs, Fr, except H). Soft, highly reactiveo Only found in nature combined in compounds (NaCl), never as free elements- Group 2Ao Elements of the second main group (Be, Mg, Ca, Sr, Ba, Ra) are composed entirely of metals that occur naturally only in compounds.o Except for Be these elements react with H2O to produce basis solutions o Most of these oxides form alkaline solutions; hence they are known as the Alkaline Earth Metalso Mg and Ca are the 7th and 5th most abundant elements in the earth’s crust
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