10/11/2013111A188A11H1.0079722APeriodic Table133A144A155A166A177A2He4.002623Li6.9394Be9.01225B10.8116C12.01127N14.00678O15.99949F18.998410Ne20.179311Na22.989812Mg24.30533B44B55B66B77B898B10 111B122B13Al26.981514Si28.08615P30.973816S32.06417Cl35.45318Ar39.948419K39.10220Ca40.0821Sc44.95622Ti47.9023V50.94224Cr51.99625Mn54.938026Fe55.84727Co58.933228Ni58.7129Cu63.5430Zn65.3731Ga65.3732Ge72.5933As74.921634Se78.9635Br79.90936Kr83.80537Rb85.4738Sr87.6239Y88.90540Zr91.2241Nb92.90642Mo95.9443Tc[99]44Ru101.0745Rh102.90546Pd106.447Ag107.87048Cd112.4049In114.8250Sn118.6951Sb121.7552Te127.6053I126.90454Xe131.30655Cs132.90556Ba137.3457La138.9172Hf178.4973Ta180.94874W183.8575Re186.276Os190.277Ir192.278Pt195.0979Au196.96780Hg200.5981Tl204.3782Pb207.1983Bi208.98084Po[210]85At[210]86Rn[ 222]787Fr[223]88Ra[ 226]89Ac[227]104Ku[260]105 106 107 108 109Mon, Oct 14• Lecture 8 (Representation)– Finish Isotopes– A Brief Introduction to Electronic Structure and the “Octet” Rule• Questions we’ll answer:– What are the consequences of atomic composition?– Chemists care about electrons a lot. What’s so interesting about electrons?10/11/20132Let’s count some particlesCobalt‐60Chlorine‐37 anionUranium‐238# protons # electrons # neutrons27 27 60 –27 = 33Copper‐63 cationCopper‐65 cation6027Co23892U3717Cl63 229Cu65 229CuAverage Atomic Mass4H31H21H1110/11/201335Average Atomic MassElement IsotopeMass of Isotope (amu)Relative AbundanceAverage Atomic Mass (amu)Hydrogen1H2H1.007822.014101.0079 Carbon12C13C12 (exact)13.0033512.01115Sulfur32S33S34S36S31.97207132.97145833.96786735.96708032.064Lithium6Li7Li6.015123 7.016005 6.94199.9844%0.0156%98.892%1.108%95.06%0.74%4.18%0.0136%7.5%92.5%Calculating Average Atomic Mass•Two isotopes of copper are naturally occurring, with copper‐63 (62.93 amu) at 69.09% and copper‐65 (64.93 amu) at 30.91%. Calculate the average atomic mass of copper.• Indium (In, average atomic mass = 114.8 amu) consists of two naturally‐occurring isotopes, indium‐113 and indium‐115. If 4.30% of a sample of indium is indium‐113, which has a mass of 112.90 amu, what is the mass of indium‐115?10/11/201347Finally…Modern Atomic Structure1. Every atom contains small, dense nucleus.2. All of the positive charge and most of the mass are concentrated in the nucleus.3. The nucleus is surrounded by a large volume of nearly empty space that makes up the rest of the atom.4. The rest of the atom is thinly populated by electrons, the total charge of which exactly balances the positive charge of the nucleus.5. Research in the decade or so following the gold‐foil experiment suggested that the nucleus contained two kinds of particles:If an atom was the size of a baseball stadium, the nucleus would be the size of a fly on home plate.~300 pm~0.01 pmLight = Electromagnetic Radiation• Light (aka EM radiation) is a form of energy. • We can model light energy as a wave oscillating through space.• Different regions of the EM spectrum are characterized by different wavelengths.• long wavelength = low energy• short wavelength = high energyThe light that you can see comprises a tiny fraction of the EM spectrum. Chemical processes in the sun release energy in every region of the EM spectrum.10/11/20135Emission SpectraEM radiation emitted from a white‐light source contains all wavelengths. It emits a continuousspectrum.In contr ast, the emission from excited atoms is discrete.Atomic Emission and AbsorbanceAtoms can emit light only at specific, discrete wavelengths.They can absorb light only at these same discrete wavelengths.The energy that an atom can absorb/emit is quantized.10/11/20136C (Z = 6)H (Z = 1)Electron Structure in Atoms• Electrons in atoms are arranged in energy levels that are “quantized.” (electrons can only have discrete amounts of energy)• Electronic energy levels are filled in order from lowest to highest energy.• Only a certain number of electrons are allowed in a given energy level.energyn= 1n= 2n= 3n= 4n= 5Cl (Z = 17)=“valence” electron=“core” electronThe electrons in the highest energy level are referred to as the “valence” electrons.Group Number = Valence ElectronsLi (Z = 3)H (Z = 1) Na (Z = 11)=“valence” electron=“core” electronN(Z = 7) P(Z = 15)Group 1A elements all have onevalence electron.Group 5A elements all have fivevalence electrons.10/11/20137Period Element Atomic Number Group Number n = 1n =2 n = 3n = 4HHeLiBeBCNOFNeNaMgAlSiPSClAr123121212345678345678123411125678910131415161718121212345678345678222222222222222288888888Atoms Strive for “Nobility”K(Z = 19)K+(Z = 19)Ar (Z = 18)loss of electronCompare to argon…O(Z = 8)gain two electronsO2–(Z = 8) Ne (Z = 10)Compare to neon…The driving force for the formation of monatomic ions is the attainment of a complete “octet” of electrons in the valence shell.10/11/20138Reading the Periodic Table“B” groups“A” groups13 4 5 6 7 8 9 10 11 12 13 14 15 16 17 181A3B 4B 5B 6B 7B 8B 1B 2B3A 4A 5A 6A 7A 8ANumber of electrons increases with Z: • left to right across a period, •