ch04---the-electronic-structure-of-atoms.ppt

New Way Chemistry for Hong Kong A-Level Book 11Chapter 4The Electronic Structure of Atoms4.1The Electromagnetic Spectrum4.2 Deduction of Electronic Structure from Ionization Enthalpies4.3 The Wave-mechanical Model of the Atom4.4 Atomic OrbitalsNew Way Chemistry for Hong Kong A-Level Book 12The Electronic Structure of AtomsNiels BohrBohrs Model of H atom Chapter 4 The electronic structure of atoms(SB p.90)New Way Chemistry for Hong Kong A-Level Book 13The Electronic Structure of AtomsNiels BohrBohrs Model of H atom Chapter 4 The electronic structure of atoms(SB p.90)New Way Chemistry for Hong Kong A-Level Book 14 The Electromagnetic Spectrum4.1 The Electromagnetic Spectrum(SB p.91)New Way Chemistry for Hong Kong A-Level Book 15Continuous spectrum of white lightFig.4-5(a)4.1 The Electromagnetic Spectrum(SB p.92)New Way Chemistry for Hong Kong A-Level Book 16Line Spectrum of hydrogen4.1 The Electromagnetic Spectrum(SB p.93)Fig.4-5(b)New Way Chemistry for Hong Kong A-Level Book 17The Emission Spectrum of Atomic HydrogenUVVisibleIR4.1 The Electromagnetic Spectrum(SB p.93)New Way Chemistry for Hong Kong A-Level Book 18Interpretation of the Atomic Hydrogen Spectrum4.1 The Electromagnetic Spectrum(SB p.94)New Way Chemistry for Hong Kong A-Level Book 19Interpretation of the Atomic Hydrogen Spectrum4.1 The Electromagnetic Spectrum(SB p.94)New Way Chemistry for Hong Kong A-Level Book 110Interpretation of the Atomic Hydrogen Spectrum4.1 The Electromagnetic Spectrum(SB p.94)New Way Chemistry for Hong Kong A-Level Book 111Bohr proposed for a hydrogen atom:1.An electron in an atom can only exist in certain states characterized by definite energy levels (called quantum).2.Different orbits have different energy levels.An orbit with higher energy is further away from the nucleus.3.When an electron jumps from a higher energy level(of energy E1)to a lower energy level(of energy E2),the energy emitted is related to the frequency of light recorded in the emission spectrum by:E=E1-E2=h4.1 The Electromagnetic Spectrum(SB p.95)New Way Chemistry for Hong Kong A-Level Book 1124.1 The Electromagnetic Spectrum(SB p.96)How can we know the energy levels are getting closer and closer together?New Way Chemistry for Hong Kong A-Level Book 1134.1 The Electromagnetic Spectrum(SB p.97)E=E1-E2=hPlanck s constantFrequency of light emittedNew Way Chemistry for Hong Kong A-Level Book 114 Emission spectrum of hydrogenAbsorption spectrum of hydrogendark background(photographic plate)bright linesbright background(photographic plate)dark lines4.1 The Electromagnetic Spectrum(SB p.97)New Way Chemistry for Hong Kong A-Level Book 115Production of the Absorption SpectrumAbsorption spectrum of hydrogen4.1 The Electromagnetic Spectrum(SB p.97)bright background(photographic plate)dark linesNew Way Chemistry for Hong Kong A-Level Book 116Convergence Limits and IonizationWhat line in the H spectrum corresponds to this electron transition(n=n=1)?Last line in the Lyman SeriesFor n=n=1:4.1 The Electromagnetic Spectrum(SB p.97)H(g)H+(g)+e-New Way Chemistry for Hong Kong A-Level Book 117The Uniqueness of Atomic Emission SpectraNo two elements have identical atomic spectraatomic spectra can be used to identify unknown elements.4.1 The Electromagnetic Spectrum(SB p.99)New Way Chemistry for Hong Kong A-Level Book 118Ionization EnthalpyIonization enthalpy(ionization energy)of an atom is the energy required to remove one mole of electrons from one mole of its gaseous atoms to form one mole of gaseous positive ions.The first ionization enthalpy M(g)M+(g)+e-H=1st I.E.The second ionization enthalpy M+(g)M2+(g)+e-H=2nd I.E.4.2 Deduction of Electronic Structure from Ionization Enthalpies(p.100)New Way Chemistry for Hong Kong A-Level Book 119Evidence of Shells shells4.2 Deduction of Electronic Structure from Ionization Enthalpies(p.101)New Way Chemistry for Hong Kong A-Level Book 120Evidence of Sub-shells4.2 Deduction of Electronic Structure from Ionization Enthalpies(p.102)2,12,22,32,42,52,62,72,8 subshellsNew Way Chemistry for Hong Kong A-Level Book 121Bohrs Atomic Model and its LimitationsBohr considered the electron in the H atom(a one-electron system)moves around the nucleus in circular orbits.Basing on classical mechanics,Bohr calculated values of frequencies of light emitted for electron transitions between such orbits.The calculated values for the frequencies of light matched with the data in the emission spectrum of H.4.3 The Wave-mechanical Model of the Atom(p.104)New Way Chemistry for Hong Kong A-Level Book 122Bohrs Atomic Model and its LimitationsBohr tried to apply similar models to atoms of other elements(many-electron system),e.g.Na atom.Basing on classical mechanics,Bohr calculated values of frequencies of light emitted for electron transitions between such orbits.The calculated values for the frequencies of light did NOT match with the data in the emission spectra of the elements.The electron orbits in atoms may NOT be simple circular path.4.3 The Wave-mechanical Model of the Atom(p.104)New Way Chemistry for Hong Kong A-Level Book 123Wave Nature of ElectronsA beam of electrons shows diffraction phenomenonElectrons possess wave properties(as well as particle properties).4.3 The Wave-mechanical Model of the Atom(p.104)New Way Chemistry for Hong Kong A-Level Book 124Wave Nature of ElectronsSchrdinger used complex differential equations/wave fucntions to describe the wave nature of the electrons inside atoms(wave mechanic model).The solutions to the differential equations describes the orbitals of the electrons inside the concerned atom.An orbital is a region of space having a high probability of finding the electron.4.3 The Wave-mechanical Model of the Atom(p.104)New Way Chemistry for Hong Kong A-Level Book 125Quantum NumbersElectrons in orbitals are specified with a set of numbers called Quantum Numbers:1.Principal quantum number(n)n=1,2,3,4,.2.Subsidiary quantum number(l)l=0,1,2,3,n-1 s p d f3.Magnetic quantum number(m)m=-l,0,l4.Spin quantum number(s)s=+,-The solutions of the wave functions are the orbitals-which are themselves equations describing the electrons.4.3 The Wave-mechanical Model of the Atom(p.104)New Way Chemistry for Hong Kong A-Level Book 1264.3 The Wave-mechanical Model of the Atom(p.105)Principal quantum number(n)Subsidiary quantum number(l)Number of orbitals(2l+1)Symbol of orbitalsMaximum number of electrons held1011s2201132s2p26 30121353s3p3d56104012313574s4p4d4f2610148 18 32New Way Chemistry for Hong Kong A-Level Book 127Each orbital can accommodate 2 electrons with opposite spin.1s2s2p3s3p3d4s4.3 The Wave-mechanical Model of the Atom(p.105)New Way Chemistry for Hong Kong A-Level Book 128The s Orbitals4.4 Atomic Orbitals(p.107)New Way Chemistry for Hong Kong A-Level Book 129The s Orbitals4.4 Atomic Orbitals(p.107)New Way Chemistry for Hong Kong A-Level Book 130The p Orbitals4.4 Atomic Orbitals(p.109)New Way Chemistry for Hong Kong A-Level Book 131