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Created by C. IppolitoOctober 2006
Electron Configurations
Objectives:1. explain the use of wave-mechanics in atomic theory2. describe the wave-mechanical model of the atom3. locate electrons in energy levels, sublevels, and orbitals4. make orbital diagrams and write electron configurations for
elements with atomic numbers from 1 through 38
Created by C. IppolitoOctober 2006
Classical (Newtonian) Mechanics
laws of motion developed by Isaac Newton explains motion of objects on earth and
solar system can explain behavior of some gases used in Bohr model
• jumping contradicts smooth continuous changes in kinetic energy
Created by C. IppolitoOctober 2006
Spectroscopy
studies the behavior of substances exposed to a continuous exciting energy
elements release absorbed energy as lightLIGHT
electromagnetic energy in the form of a wave• Frequency (f) cycles/second hertz • Wavelength (lambda = λ) nanometers• Amplitude height of peaks and troughs
– velocity = f λ for light velocity = c (3.0 x 108 m/s)
Created by C. IppolitoOctober 2006
Line Spectra
unique set of light wavelengths released by excited substance returning to ground state
• sodium (Na+)• potassium (K+)• barium (Ba+2)• strontium (Sr+2)• lithium (Li+1)
Created by C. IppolitoOctober 2006
Wave (Quantum) Mechanics
studies the motion of relatively small particles that travel at relatively fast speeds Max PlanckMax Planck
• light energy not released continuously• released in small spurts
– quantumquantum – packet of electromagnetic energy– photonphoton – packet of light energy
• energy is related to frequency of light– f = c/λ c = 3.00 x 108 m/s– E = hf– h= 6.6 x 10-34 j/hz
Created by C. IppolitoOctober 2006
Photoelectric Effect
refers to the emission of electrons from certain substances when exposed to light of a particular frequency Albert EinsteinAlbert Einstein
• wins Nobel Prize if energy from light is enough to free electron it will; any additional energy does not free additional electrons
Created by C. IppolitoOctober 2006
De Broglie’s Hypothesis
combines Einstein and Planck equation predicts “wave length” of particle with known mass
and velocity combined Planck and Einstein equation
• E = mc2 and E = hf so that mc2 = hf replaced f with v/λ wave frequency is velocity/wavelength
• mv2 = hv/λ solves for wavelength
• λ = h/mv
Wave-Particle Duality of NatureWave-Particle Duality of Nature waves can act like particles and particles can act like waves
Created by C. IppolitoOctober 2006
Measuring Position and Momentum
Werner HeisenbergWerner Heisenberg Heisenberg Uncertainty Heisenberg Uncertainty
PrinciplePrinciple• exact position and exact momentum
CANNOT be determined at the same time
• look at object to see it (light to eyes)– small objects like electron
• light bouncing off it changes its velocity
can never know where an electron will be or where it is going
Created by C. IppolitoOctober 2006
Schrodinger’s Work
Erwin SchrodingerErwin Schrodinger electron a wave develops an equation using quantum number
• describes the probable location as an ELECTRON CLOUDELECTRON CLOUD
Four Quantum NumbersFour Quantum Numbers used to describe electron behavior in complex atomsused to describe electron behavior in complex atoms
Created by C. IppolitoOctober 2006
Principle Quantum Number (n)
describes energy levels
used find maximum number of electrons 2n2 = maximum
electrons on level n2 = number of
orbitals
# n2 Orbitals 2n2 # of e-
1 (1)2 1 2(1)2 2
2 (2)2 4 2(2)2 8
3 (3)2 9 2(3)2 18
4 (4)2 16 2(4)2 32
Created by C. IppolitoOctober 2006
Second Quantum Number (l)
complex atoms with more than one level have higher level divided into sublevelssublevels s – lowest sublevel – “sharp” p – second sublevel – “principal” d – third sublevel – “diffuse” f – fourth sublevel –”fundamental”
Created by C. IppolitoOctober 2006
Third Quantum Number (m)
represents subdivisions in the sublevels – orbitals s – one electron pair p – three electron pairs d – five electron pairs f – seven electron pairs
Created by C. IppolitoOctober 2006
Distribution of Electrons
Pauli’s Exclusion PrinciplePauli’s Exclusion Principle no two electrons can have exactly the
same quantum numbers• Fourth Quantum Number
– describes magnetic spin
Hund’s RuleHund’s Rule electrons prefer to occupy an empty orbital
before it will occupy one as a pair
Created by C. IppolitoOctober 2006
Diagonal Rule
atoms with high atomic numbers do not fill orbitals in order
Created by C. IppolitoOctober 2006
Electron Dot Diagrams
chemical properties depend on valance (outermost) electrons element symbol represents nucleus and all
lower level electrons write out electron configuration draw dots on sides to represent electrons
in orbitals (basically last level of Bohr diagram)