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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 Spectrum

From www.lcse.umn.edu/specs/labs/images/spectrum.gif

Electromagnetic SpectrumFrequency and wavelength are inversely

related, as demonstrated by the equation

c=λνc-speed of light constant-2.9979x108m/s λ-wavelength(m)ν-frequency(Hz or s-1)

Quantum TheoryEinstein—Light behaves as if it consists of

quantized energy packets, meaning that energy can have only certain allowed values given by the equation

Ephoton=hνEphoton-(J)h-Planck’s constant-6.626x10-34 J-secν-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 number

Each 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

λ=h/mvλ-wavelength(m) h-Planck’s constant-6.626x10-34 J-s m-mass of particle(kg) (e-=9.11x10-31kg) v-velocity (m/s)

Bohr’s 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 configuration—use 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 n

For 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- sp2

Tetrahedral-4 domains, sp3

Trigonal 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 Bond

Covalent bonds formed from end to end overlap of s orbitals

Pi Bond Bond 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 Order

Bond Order = ½(# of electrons bonding - # of electrons anti-bonding)

The principle of anti-bonding sets molecular orbital theory apart from valence bond theory

Paramagnetism and Diamagnetismparamagnetism—an attraction of a molecule

by a magnetic field due to unpaired electrons

diamagnetism—a 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?a.NH3

b.SF6

c.ClF3