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Unit 6B: Atomic Structure and Bonding Theory. By Lauren and Joe. Electromagnetic Spectrum. From www.lcse.umn.edu/specs/labs/images/spectrum.gif. Electromagnetic Spectrum. Frequency and wavelength are inversely related, as demonstrated by the equation c=λν - PowerPoint PPT Presentation

Transcript of Unit 6B: Atomic Structure and Bonding Theory

• By Lauren and Joe

• Electromagnetic SpectrumFrom www.lcse.umn.edu/specs/labs/images/spectrum.gif

• Electromagnetic SpectrumFrequency and wavelength are inversely related, as demonstrated by the equationc=c-speed of light constant-2.9979x108m/s -wavelength(m)-frequency(Hz or s-1)

• Quantum TheoryEinsteinLight behaves as if it consists of quantized energy packets, meaning that energy can have only certain allowed values given by the equationEphoton=hEphoton-(J)h-Plancks constant-6.626x10-34 J-sec-frequency (Hz or s-1)

• Another Equation to Remember

Ephoton=Eremove electron/threshold + Ekinetic

• Quantum Numbersn-principal quantum number (shell)i.e. 3s, n=3

l-azimuthal quantum number (sub-shell)The value of l corresponds to the sub-shell of the orbitals=0, p=1, d=2, f=3i.e. if n=3, can have 3s, 3p, 3d. Accordingly, you can have l values 0, 1, and 2.

• More Quantum Numbers!ml-magnetic quantum numberEach orbital has number from L to +Li.e. 3p4 , occupies 1st orbital, ml= -1

ms-magnetic spin quantum numberValue is 1/2If electron points up, +1/2If electron points down, -1/2i.e. 3p4, points down, ms= -1/2

• DeBroglie WavelengthMatter has a characteristic wavelength that depends on its momentum, mv=h/mv-wavelength(m) h-Plancks constant-6.626x10-34 J-s m-mass of particle(kg) (e-=9.11x10-31kg) v-velocity (m/s)

• Bohrs ModelA model of the hydrogen atom that explains its line spectrum

Light emitted when the electron drops from a higher energy state to a lower energy state

Light must be absorbed to excite the electron from a lower energy state to a higher energy state

• Electron ConfigurationUse the periodic table to write electron configurationsCore electron configurationuse largest noble gas that is smaller than atom/ion, then write additional electrons

Remember that each orbital can hold 2 electrons each

Place 1 electron in each orbital before putting a second one

Electron configurations are most stable when the orbitals are full or half-full

• Electron ConfigurationD Block (Transition metals)-5 orbitals @ 2 electrons each=10 electronsD block 1 behind s/p block

F Block7 orbitals @2 electrons each=14 electronsF block 1 behind D block, 2 behind s/p block

• Electron Configuration of IonsWhen determining configurations for cations, remove electrons first from the orbital with the largest quantum number nFor example, Sn=[Ar] 4s23d104p2 Sn3+= =[Ar]4s13d10

• HybridizationMixing of s, p, and d orbitals to form hybrid orbitals

A particular mode of hybridization corresponds with each of the five common electron-domain geometriesnote: electron domain geometry is arrangement of electron domains around a central atom. Each bond, whether it is single, double, or triple, and each lone pair is one electron domain.

• HybridizationLinear-2 electron domains-sp hybridizationTrigonal planar-3 electron domains- sp2Tetrahedral-4 domains, sp3Trigonal bipyramidal- 5 domains, sp3dOctahedral- 6 domains, sp3d2

• Valence Bond TheoryBonds form when atomic orbitals overlap between two atomsThe greater the overlap between two orbitals, the stronger the bondSigma BondCovalent bonds formed from end to end overlap of s orbitalsPi BondBond formed from the sideways overlap of p orbitals

• Molecular Orbital TheoryElectrons exist in allowed energy states called molecular orbitals (MOs)Like an atomic orbital, an MO can hold two electrons of opposite spinOccupation of bonding MOs favors bond formationOccupation of antibonding MOs (denoted with an *) is unfavorable

• Molecular Orbital TheoryBond OrderBond Order = (# of electrons bonding - # of electrons anti-bonding)The principle of anti-bonding sets molecular orbital theory apart from valence bond theory

• Paramagnetism and Diamagnetismparamagnetisman attraction of a molecule by a magnetic field due to unpaired electrons

diamagnetisma weak repulsion from a magnetic field by paired electrons

• Question 1What is the core electron configuration of Pb3+?

• Question 2What type of hybridization does the central atom in the following compounds assume?NH3SF6ClF3