Created by C. Ippolito October 2006 Electron Configurations Objectives: 1. explain the use of wave-mechanics in atomic theory 2. describe the wave-mechanical

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


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


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)


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)


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


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


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


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


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


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


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”


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


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


Diagonal Rule

atoms with high atomic numbers do not fill orbitals in order


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)


Electron Configuration Samples

H – 1s1

He – 1s2

O – 1s2 2s2 2p4

Ca – 1s2 2s2 2p6 3s2 3p6 4s2

Cd - 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10

Documents

Created by C. Ippolito October 2006 Electron Configurations Objectives: 1. explain the use of wave-mechanics in atomic theory 2. describe the wave-mechanical