Light, Energy, and MoreLight, Energy, and MoreOctober 23, 2007October 23, 2007

Chemistry Chemistry

Recap…Recap…

Electromagnetic Electromagnetic SpectrumSpectrum

High EnergyHigh Energy Low EnergyLow Energy Wave Nature of Wave Nature of

LightLight

What’s Going On Here?What’s Going On Here?

When we heat metal what When we heat metal what happens?happens?

Does the wave model of light explain Does the wave model of light explain these changes?these changes?• Does not explain different wavelengths and Does not explain different wavelengths and

frequencies at different temperaturesfrequencies at different temperatures What is light?What is light?

• Radiation….what is radiation?Radiation….what is radiation? Particles or rays of energyParticles or rays of energy

What is temperature anyways?What is temperature anyways?• The measure of the average kinetic energy of The measure of the average kinetic energy of

the particles in an objectthe particles in an object• Kinetic Energy vs. Potential EnergyKinetic Energy vs. Potential Energy

Too many questions….Too many questions….

Max Planck (1900)Max Planck (1900)

German PhysicistGerman Physicist Began to look for Began to look for

answersanswers Matter can only Matter can only

gain or lose energy gain or lose energy in small quantized in small quantized amountsamounts

What’s quantized?What’s quantized?

Vocab Word!!!Vocab Word!!!

QUANTUMQUANTUM• Minimum amount of energy that can be Minimum amount of energy that can be

gained or lost by an atomgained or lost by an atom• The emitted light from a glowing metal The emitted light from a glowing metal

is a ENERGY…this energy is quantizedis a ENERGY…this energy is quantized

If energy is now quantized…how If energy is now quantized…how can we determine the amount of can we determine the amount of

energy of a quantum?energy of a quantum?

What is energy measured in?What is energy measured in? What are we observing?What are we observing? What happens to the color when we What happens to the color when we

increase the temperature (energy)?increase the temperature (energy)?• Proportional or inversely proportional?Proportional or inversely proportional?

Now we need a constant…Now we need a constant…• Planck’s constant, h=6.626 x 10^-34 J*sPlanck’s constant, h=6.626 x 10^-34 J*s

Time to put these words into action!Time to put these words into action!

What is the frequency and What is the frequency and wavelength electromagnetic wavelength electromagnetic radiation that emits 1.68 x 10^-17 J radiation that emits 1.68 x 10^-17 J of energy? What type of of energy? What type of electromagnetic radiation is this?electromagnetic radiation is this?

Wavelength= 1.18 x 10^-8 mWavelength= 1.18 x 10^-8 m Ultraviolet radiationUltraviolet radiation

Some questions to answer…Some questions to answer…

What is the color we see?What is the color we see? What happens to the energy of the What happens to the energy of the

radiation when we increase the radiation when we increase the frequency, v, of the radiation frequency, v, of the radiation emitted?emitted?

Iron at room temp…color and E?Iron at room temp…color and E? Iron with a little heat…color and E?Iron with a little heat…color and E? Iron with lots of heat…color and E?Iron with lots of heat…color and E?

According to Planck’s Theory…According to Planck’s Theory… If we have a given v, If we have a given v,

matter can emit or absorb matter can emit or absorb E only in whole number E only in whole number multiples of hv (1hv, 2hv, 3 multiples of hv (1hv, 2hv, 3 hv…)hv…)

Matter can ONLY have Matter can ONLY have specific amounts of energyspecific amounts of energy

Wall of kids building blocksWall of kids building blocks• We can only add or take We can only add or take

away in increments of away in increments of whole blocks…we cannot whole blocks…we cannot remove half a blockremove half a block

The Big Mystery of the 1900’s…The Big Mystery of the 1900’s…

The Photoelectric The Photoelectric Effect…Effect…• What caused these What caused these

color changes in color changes in metals???metals???

Photoelectric EffectPhotoelectric Effect

Electrons (photoelectrons) are Electrons (photoelectrons) are emitted from a metal’s surface when emitted from a metal’s surface when a light of a certain frequency shines a light of a certain frequency shines on the surfaceon the surface

Certain specific amounts of energy Certain specific amounts of energy (what’s this called???) needed to (what’s this called???) needed to knock out electrons from metal knock out electrons from metal atoms. atoms.

Albert Einstein (1905)Albert Einstein (1905)

Added onto Planck’s Added onto Planck’s Theory…Theory…

Called the electron’s Called the electron’s emitted, PHOTONS (the emitted, PHOTONS (the little energy packets little energy packets Planck called quantums)Planck called quantums)

Now… ENow… Ephoton photon = hv= hv

Planck paved the Planck paved the way for the way for the explanation behind explanation behind the mysterythe mystery

But some one else But some one else came into the came into the picture…picture…

Now light is not just a wave…Now light is not just a wave…

Einstein’s Dual Nature of LightEinstein’s Dual Nature of Light• Particle and wave characteristicsParticle and wave characteristics• Light is a beam of tiny particles, called Light is a beam of tiny particles, called

photons, acting like a wavephotons, acting like a wave

NEW WORD!!!NEW WORD!!!

PhotonPhoton A particle of electromagnetic A particle of electromagnetic

radiation with no mass that carries a radiation with no mass that carries a quantum of energyquantum of energy

What Einstein added…What Einstein added…

Energy of a photon has a minimum Energy of a photon has a minimum or threshold value to eject or threshold value to eject photoelectronsphotoelectrons

What must happen for the What must happen for the photoelectric effect to occur?photoelectric effect to occur?• Energy of a photon (particle of EM Energy of a photon (particle of EM

radiation) must have the minimum radiation) must have the minimum energy requirement to free the electron energy requirement to free the electron from the atom of metal from the atom of metal

Mystery Solved!Mystery Solved! No matter how long a No matter how long a

light of a certain light of a certain frequency is shone on frequency is shone on metal (intensity), metal (intensity), electrons will not be electrons will not be ejected unless the ejected unless the minimum amount of minimum amount of energy is shone.energy is shone.

Silver metalSilver metal• Photoelectrons ejected Photoelectrons ejected

when a light with a when a light with a frequency of at least frequency of at least 1.14 x 10^15 Hz or 1.14 x 10^15 Hz or greater is usedgreater is used

Sodium metalSodium metal• Red lightRed light• Violet lightViolet light

Revised Planck’s Work…Revised Planck’s Work…

Einstein piggy-backed off of Planck’s Einstein piggy-backed off of Planck’s Theory and we now have…..Theory and we now have…..

Photon

Time to do a little work….Time to do a little work….

Tiny water drops in the air disperse Tiny water drops in the air disperse the white light of the sun into a the white light of the sun into a rainbow. What is the Energy oa a rainbow. What is the Energy oa a photon from the violet portion of the photon from the violet portion of the rainbow if it has a frequency of rainbow if it has a frequency of 7.23x10^14 Hz?7.23x10^14 Hz?

E=4.79 x 10^-19 JE=4.79 x 10^-19 J• Energy in a photon of violet lightEnergy in a photon of violet light

A couple more… A couple more…

A photon has an energy of 2.93 x A photon has an energy of 2.93 x 10^-25 J. What is its frequency? 10^-25 J. What is its frequency? What type of electromagnetic What type of electromagnetic radiation is the photon?radiation is the photon?

V=4.42 x 10^8 HzV=4.42 x 10^8 Hz TV or FM wavesTV or FM waves

Practice makes perfect… Practice makes perfect… What is the energy of each photon in What is the energy of each photon in

the following types of radiation?the following types of radiation?• 6.32 x 10^20 Hz6.32 x 10^20 Hz• 9.50 x 10^13 Hz9.50 x 10^13 Hz• 1.05 x 10^16 Hz1.05 x 10^16 Hz

What types of radiation are each?What types of radiation are each? 4.19 x 10^-13 J gamma or x-ray4.19 x 10^-13 J gamma or x-ray 6.29 x 10^20 J infrared6.29 x 10^20 J infrared 6.96 x 10^-18 J ultraviolet6.96 x 10^-18 J ultraviolet

How does this work? How does this work? (Neon Signs)(Neon Signs)

What do we know about neon What do we know about neon signs?signs?

Electricity is passed through tube full of Electricity is passed through tube full of neon gasneon gas

Neon atoms in tube absorb this energyNeon atoms in tube absorb this energy• What happens when something absorbs What happens when something absorbs

energy?energy? Neon atoms in tube become excitedNeon atoms in tube become excited

• Stable of Unstable?Stable of Unstable?• What happens when something is unstable?What happens when something is unstable?• What do we see released energy as?What do we see released energy as?

Electromagnetic radiation…visible light!!!Electromagnetic radiation…visible light!!!

EM spectrum EM spectrum What happens when we pass sunlight What happens when we pass sunlight

through a prism?through a prism?• Continuous spectrum of colorsContinuous spectrum of colors• ROYGBIVROYGBIV

What happens when we pass light What happens when we pass light from neon gas or hydrogen gas from neon gas or hydrogen gas

through prism? through prism?

Separation of colorsSeparation of colors Discontinuous spectrumDiscontinuous spectrum This is called…This is called…

ATOMIC EMISSION SPECTRUMATOMIC EMISSION SPECTRUM(AES)(AES)

AES of an element is the set of frequencies AES of an element is the set of frequencies of the electromagnetic radiation emitted of the electromagnetic radiation emitted by the atoms of that elementby the atoms of that element

Individual lines of colorIndividual lines of color Only certain lines of color appear for Only certain lines of color appear for

certain elements…certain elements…• What does this mean…????What does this mean…????

Every element has a unique AESEvery element has a unique AES Why is this important?Why is this important?

Hydrogen AtomHydrogen Atom

Why did scientists want to use Why did scientists want to use hydrogen?hydrogen?• How many protons?How many protons?• How many electrons?How many electrons?• Do you think it is easy to use?Do you think it is easy to use?• Check out the AES of hydrogen gas…Check out the AES of hydrogen gas…

Neils Bohr (1913)Neils Bohr (1913)

Danish PhysicistDanish Physicist Worked with Worked with

RutherfordRutherford Quantum Model of Quantum Model of

Hydrogen atomHydrogen atom• Predicted lines of Predicted lines of

Hydrogen AESHydrogen AES

Hydrogen has only one electron but Hydrogen has only one electron but why do we get different colored lines why do we get different colored lines on AES???on AES???• We get hydrogen atoms excited…We get hydrogen atoms excited…• Electrons move to excited levelsElectrons move to excited levels

H has certain allowable energy H has certain allowable energy states….states….• The lowest energy state is called the The lowest energy state is called the

GROUND STATEGROUND STATE

Bohr’s Hydrogen Orbits…Bohr’s Hydrogen Orbits…

He related H’s energy states to the motion He related H’s energy states to the motion of an electron in an atomof an electron in an atom

Single electron in moves around nucleus in Single electron in moves around nucleus in circular orbitscircular orbits

Smaller orbit, smaller radius, closer to Smaller orbit, smaller radius, closer to nucleus means…?nucleus means…?• Lower energy levelLower energy level

Larger orbit, larger radius, farther from the Larger orbit, larger radius, farther from the nucleus means…?nucleus means…?• Higher energy levelHigher energy level

Bohr’s Quantum ModelBohr’s Quantum Model

Assigned quantum numbers, n, to Assigned quantum numbers, n, to each orbiteach orbit

Calculated orbits radiusCalculated orbits radius• Chart on page 127Chart on page 127

11stst orbit orbitn=1 (first energy level)n=1 (first energy level) 22ndnd orbit orbitn=2 (second energy level)n=2 (second energy level) 33rdrd orbit orbitn=3 (third energy level)n=3 (third energy level)

When we add energy, what When we add energy, what happens to electron?happens to electron?

Electron excitedElectron excited Moves to next energy levelMoves to next energy level Excited=?Excited=?

• unstableunstable What happens when something is What happens when something is

unstable?unstable?• Wants to get back to being stableWants to get back to being stable• Releases energyReleases energy• Goes back down to lower energy levelGoes back down to lower energy level

Photon is emitted corresponding to the 2 Photon is emitted corresponding to the 2 different energy levels associated with the different energy levels associated with the 2 orbits2 orbits

NEW EQUATIONNEW EQUATION

/_\ E= E /_\ E= E higher e- orbithigher e- orbit - E - E lower e- orbit lower e- orbit =E =E photonphoton=hv=hv Only certain energies are possible so Only certain energies are possible so

only certain frequencies, v, of EM only certain frequencies, v, of EM radiation are emittedradiation are emitted

Lets look at the AES of Hydrogen…Lets look at the AES of Hydrogen…

•How many lines are there?

•So how many different types of radiations are we seeing?

•There are 4 electron transitions account for lines in the hydrogen spectrum

•Going from 3rd orbital to 2nd orbital…

•Going from 4th orbital to 2nd orbital…

•Going from 5th orbital to 2nd orbital…

•Going from 6th orbital to 2nd orbital…

Names for these lines…Names for these lines…

Balmer SeriesBalmer Series• The 4 visible color linesThe 4 visible color lines• Electrons that drop into n=2Electrons that drop into n=2

Other electrons transitions not visibleOther electrons transitions not visible• Lyman seriesLyman series

Ultraviolet lightUltraviolet light Electrons drop into n=1Electrons drop into n=1

• Paschen seriesPaschen series Infrared Infrared Electrons drop into n=3Electrons drop into n=3

Problems with Bohr’s ModelProblems with Bohr’s Model

Predicted AES lines of H but not any Predicted AES lines of H but not any other elementsother elements

Did not account for all chemical Did not account for all chemical behaviorbehavior

Big problem…Big problem…• Electrons don’t move in circular orbitsElectrons don’t move in circular orbits• Time for a new model…Time for a new model…

Louis De Broglie (1924)Louis De Broglie (1924)

French physics French physics graduate studentgraduate student

Proposed idea that Proposed idea that accounted for the accounted for the fixed energy levels in fixed energy levels in Bohr’s modelBohr’s model

If waves can have particle like If waves can have particle like characteristics, then can characteristics, then can

particles, such as electrons, have particles, such as electrons, have wave like characteristics???wave like characteristics???

What he knew…What he knew…

Electrons have wavelike motion Electrons have wavelike motion (because it’s a particle)(because it’s a particle)

An electron had restricted orbitsAn electron had restricted orbits Each orbit had a fixed radius from Each orbit had a fixed radius from

the nucleusthe nucleus Are a wide variety of wavelengths, Are a wide variety of wavelengths,

frequencies, and energies possible?frequencies, and energies possible?

No…there could only be allowed No…there could only be allowed certain possible frequencies, certain possible frequencies, wavelengths, and energies in an wavelengths, and energies in an atomatom

De Broglie came up with an equation De Broglie came up with an equation for the wavelength of a particle of for the wavelength of a particle of mass (m) moving at velocity (v).mass (m) moving at velocity (v).

De Broglie’s EquationDe Broglie’s Equation

What does this equation do?What does this equation do?

What are we using?What are we using?• WavelengthWavelength• Planck’s constantPlanck’s constant• Mass of the particleMass of the particle• VelocityVelocity

Tells us that all moving particles Tells us that all moving particles have wave-like characteristicshave wave-like characteristics

Food for thought…Food for thought…

Cars?Cars? Baseball?Baseball? Do these have Do these have

wavelike wavelike characteristics? characteristics? Why or why not?Why or why not?

Yes…let’s look at the equation…Yes…let’s look at the equation…

λλ= = h h

mvmv

The car and the baseball do have a velocity and a The car and the baseball do have a velocity and a mass…mass…

Using De Broglie’s equation we do get a Using De Broglie’s equation we do get a wavelength for the movement of a baseball and a wavelength for the movement of a baseball and a car…car…

Let’s try the calculation…Let’s try the calculation…

Problem time…Problem time…

Mass of car= 910 kgMass of car= 910 kg Velocity of car= 25m/sVelocity of car= 25m/s What is the wavelength of the moving car?What is the wavelength of the moving car?

• 2.9 x 10^-38 m2.9 x 10^-38 m How big is this?How big is this? Can we see or measure this wavelength?Can we see or measure this wavelength?

• No, much to small to be detected, even with No, much to small to be detected, even with the most sophisticated equipmentthe most sophisticated equipment

Another one…Another one…

Electron speed= 25 m/sElectron speed= 25 m/s Electron mass= 9.11 x 10^-28 gElectron mass= 9.11 x 10^-28 g What is the wavelength of the What is the wavelength of the

moving electron?moving electron?• 2.9 x 10^-5 m2.9 x 10^-5 m

Do you think we can measure this Do you think we can measure this wavelength and see it?wavelength and see it?• Yes, with the right equipmentYes, with the right equipment

Practice makes perfect Practice makes perfect

What is the wavelength of an What is the wavelength of an electron of mass 9.11 x 10-28 kg electron of mass 9.11 x 10-28 kg traveling at a velocity of 2.00 x 108 traveling at a velocity of 2.00 x 108 m/s? (Planck's constant = 6.63 x 10-m/s? (Planck's constant = 6.63 x 10-34 J/Hz. 34 J/Hz.

3.64 x 10-15m.3.64 x 10-15m.

Werner Heisenberg (1901-1976)Werner Heisenberg (1901-1976)

German German theoretical theoretical physicistphysicist

Drew conclusion Drew conclusion from Rutherford, from Rutherford, Bohr, and De Bohr, and De Broglie’s modelsBroglie’s models

Problem with finding the position of Problem with finding the position of an electronan electron

Helium balloon in a dark roomHelium balloon in a dark room How would you determine the How would you determine the

location of this balloon?location of this balloon? Is the balloon going to stay in the Is the balloon going to stay in the

same position?same position? Energy transferEnergy transfer What if I gave you a flashlight?What if I gave you a flashlight?

• What happens when we shine a beam of What happens when we shine a beam of light on the balloon?light on the balloon?

Photons from light that reflect off of Photons from light that reflect off of the balloon reach our eyes and tell the balloon reach our eyes and tell us where the balloon isus where the balloon is

Is there a transfer of energy?Is there a transfer of energy?• How big is the balloon compared to the How big is the balloon compared to the

photons?photons? Can we do the same thing with Can we do the same thing with

finding the location of an electron in finding the location of an electron in an atom?an atom?

Heisenberg focused on the Heisenberg focused on the interactions between photons and interactions between photons and electrons…electrons…

Heisenberg Uncertainty PrincipleHeisenberg Uncertainty Principle

It is fundamentally impossible to It is fundamentally impossible to know precisely both the velocity and know precisely both the velocity and position of a particle at the same position of a particle at the same timetime

Erwin Schrodinger (1926)Erwin Schrodinger (1926)

Austrian physicistAustrian physicist Furthered De Furthered De

Broglie’s wave-Broglie’s wave-particle theoryparticle theory

Derived equation Derived equation that treated that treated hydrogen’s electron hydrogen’s electron as a waveas a wave

Unlike Bohr’s, his fit Unlike Bohr’s, his fit well with atoms of well with atoms of different elementsdifferent elements

Quantum Mechanical Model of the Quantum Mechanical Model of the atomatom

The Quantum Mechanical ModelThe Quantum Mechanical Model

Similar to Bohr’s…Similar to Bohr’s…• Limits an electron’s energy to certain Limits an electron’s energy to certain

valuesvalues Unlike Bohr’s…Unlike Bohr’s…

• What did Bohr say about the orbit of an What did Bohr say about the orbit of an electron around the nucleus?electron around the nucleus?

• The Quantum Mechanic Model makes no The Quantum Mechanic Model makes no attempt to describe the electron’s pathattempt to describe the electron’s path

Schrodinger’s wave equationSchrodinger’s wave equation• Solutions to equation called wave Solutions to equation called wave

functionfunction Don’t worry about the equation its self…just Don’t worry about the equation its self…just

know the basics….know the basics….

• Wave functionWave function probability of finding probability of finding the electron within a particular volume the electron within a particular volume of space around the nucleusof space around the nucleus

• High probabilityHigh probability more likely to occur more likely to occur• Low probabilityLow probability less likely to occur less likely to occur

σ3/2 Zπ

11s 0

eΨ a

What the wave function tells usWhat the wave function tells us

The atomic orbital of the The atomic orbital of the electronelectron• Atomic orbitalAtomic orbital 3-D 3-D

region around nucleusregion around nucleus Fuzzy CloudFuzzy Cloud Density of the cloud at a Density of the cloud at a

given point is proportional to given point is proportional to the probability of finding the the probability of finding the electron at that pointelectron at that point

New WordNew Word OrbitalOrbital region of space where region of space where

there is a 90% probability of finding there is a 90% probability of finding an electron of a given energyan electron of a given energy

““electron cloud”electron cloud”

OrbitalOrbital

What did Bohr assign to electron What did Bohr assign to electron orbitals?orbitals?

Quantum numbersQuantum numbers Quantum Mechanical Model does the Quantum Mechanical Model does the

same…same…

Four Quantum Numbers:Four Quantum Numbers:

• Specify the “address” (zip code) of each Specify the “address” (zip code) of each electron in an atomelectron in an atom

First number…Principal Quantum First number…Principal Quantum Number Number ( ( n) n)

Energy level (associated with the electron)Energy level (associated with the electron) Size if orbitalSize if orbital

• Lowest energy level is assigned principle quantum Lowest energy level is assigned principle quantum number of 1 (n=1)number of 1 (n=1)

Ground stateGround state

• What do you think happens as we increase n?What do you think happens as we increase n?

Orbital becomes largerOrbital becomes larger

Electron spends more time farther away from the Electron spends more time farther away from the nucleusnucleus atom’s energy increases atom’s energy increases

Principle energy levels Principle energy levels contain…contain…

Energy Energy SublevelsSublevels

Principle energy level 1Principle energy level 1 single sublevel single sublevel Principle energy level 2Principle energy level 2 two sublevels two sublevels Principle energy level 3Principle energy level 3 three sublevels three sublevels What pattern do you see in the number of What pattern do you see in the number of

sublevels as we move further away from sublevels as we move further away from the nucleus?the nucleus?• They increase as n increases (the further we They increase as n increases (the further we

get from the nucleus)get from the nucleus)UPPER LEVEL

Electron’s are labeled Electron’s are labeled according to n valueaccording to n value

In atom’s with more In atom’s with more than one electron, two than one electron, two or more electron’s or more electron’s may have the same n may have the same n value value • They are in the same They are in the same

“electron shell”“electron shell”

Second quantum Second quantum numbernumber

Angular Momentum Quantum Angular Momentum Quantum Number (l) Number (l)

Each value of l corresponds to a Each value of l corresponds to a different type of orbital with a different different type of orbital with a different shapeshape

Value of n controls l (subshells Value of n controls l (subshells possible)possible)

Angular momentum numbers can equal Angular momentum numbers can equal 0, 1, 2, 3… 0, 1, 2, 3…

l=n-1l=n-1• When n=1, l=0When n=1, l=0 only one possible subshellonly one possible subshell

• When n=2, l=0,1When n=2, l=0,1 two possible subshellstwo possible subshells

What the number of l means…What the number of l means…

Corresponds to the name of the Corresponds to the name of the subshell subshell • L=0L=0 subshell s subshell s• L=1L=1 subshell p subshell p• L=2L=2 subshell d subshell d• L=3L=3 subshell f subshell f

S P D F: THE SUBLEVELSS P D F: THE SUBLEVELS Each of these 4 sublevels has a unique Each of these 4 sublevels has a unique

shapeshape Each orbital may contain at most, 2 Each orbital may contain at most, 2

electronselectrons LETTERS ORIGINATED FROM LETTERS ORIGINATED FROM

DESCRIPTIONS OF THEIR SPECTRAL LINESDESCRIPTIONS OF THEIR SPECTRAL LINES• SS sharp…spherical sharp…spherical• PP principal…dumbbell shaped principal…dumbbell shaped• DD diffuse…not all the same shape diffuse…not all the same shape• FF fundamental…not all the same shape fundamental…not all the same shape

When principle energy level n=1, then l=0, which means there When principle energy level n=1, then l=0, which means there is only a single sublevel (one orbital) which is the small, is only a single sublevel (one orbital) which is the small, spherical 1sspherical 1s

When principle energy level n=2, then l can equal 0 or 1, which When principle energy level n=2, then l can equal 0 or 1, which means that there are two sublevels (orbitals) 2s and 2pmeans that there are two sublevels (orbitals) 2s and 2p• 2s sublevel2s sublevel bigger than 1s, still sphere bigger than 1s, still sphere• 2p sublevel2p sublevel three dumbbell shaped p orbitals of equal energy three dumbbell shaped p orbitals of equal energy

called 2px, 2py, and 2pzcalled 2px, 2py, and 2pz The letters are just there to tell you what axis the electrons go on: x,y, or The letters are just there to tell you what axis the electrons go on: x,y, or

z axisz axis When the principle energy level n=3, then l can equal 0,1, or 2, When the principle energy level n=3, then l can equal 0,1, or 2,

which means that there are 3 possible sublevels: which means that there are 3 possible sublevels: • 3s, sphere, bigger than 1s and 2s3s, sphere, bigger than 1s and 2s• 3p, dumbbells3p, dumbbells• 3d3d

Each d sublevel consists 5 orbitals of equal energyEach d sublevel consists 5 orbitals of equal energy Four d orbitals have same shape but different orientationsFour d orbitals have same shape but different orientations Fifth d orbital, 3dFifth d orbital, 3dz2z2 is shaped and oriented different from the other four is shaped and oriented different from the other four

When the principle energy level n=4, then 1 can equal 0,1,2, or When the principle energy level n=4, then 1 can equal 0,1,2, or 3 which means l=n-1=4 possible sublevels:3 which means l=n-1=4 possible sublevels:• Seven f orbitals of equal energy ( 2 electrons in each orbital)Seven f orbitals of equal energy ( 2 electrons in each orbital)• 4s, sphere4s, sphere• 4p, dumbbells4p, dumbbells• 4d,4d,• 4f4f

n = # of sublevels per leveln2 = # of orbitals per levelSublevel sets: 1 s, 3 p, 5 d, 7 f

2s

2pz

2py

2px

Orbitals combine to form a spherical shape.

Remember…Remember…

1. Principal #1. Principal # energy levelenergy level

2. Ang. Mom. #2. Ang. Mom. # sublevel (s,p,d,f)sublevel (s,p,d,f)

There are two more quantum numbers (3 and 4) we will discuss next class

Third Quantum NumberThird Quantum Number

MMl specifies the orientation of the specifies the orientation of the orbital in space containing the orbital in space containing the electronelectron

Tells us whether the orbital is on the Tells us whether the orbital is on the x, y, or z axisx, y, or z axis

Fourth Quantum NumberFourth Quantum Number

MMs related to the direction of related to the direction of the electron spinthe electron spin

Tells us if electron has a Tells us if electron has a clockwise spin or counter clockwise spin or counter clockwise spinclockwise spin

Specifies orientation of Specifies orientation of electrons spin axiselectrons spin axis

Recap…Recap…

Bohr?Bohr?• Orbits explained hydrogen’s quantized Orbits explained hydrogen’s quantized

energy statesenergy states De Broglie?De Broglie?

• Dual particle and wave nature of Dual particle and wave nature of electronselectrons

Schrodinger?Schrodinger?• Wave equation predicted existence of Wave equation predicted existence of

atomic orbitals containing electronsatomic orbitals containing electrons

Electron ConfigurationElectron Configuration

Definition: arrangement of electrons in an Definition: arrangement of electrons in an atomatom

Basic rules for filling up orbital's with Basic rules for filling up orbital's with electronselectrons

Which is more stable, low energy or high Which is more stable, low energy or high energy?energy?• So which orbitals are going to be filled up first?So which orbitals are going to be filled up first?• We are going to want an arrangement that We are going to want an arrangement that

gives us the lowest possible energygives us the lowest possible energy

Ground state electron configurationGround state electron configuration

The most stable, lowest energy The most stable, lowest energy electron arrangement of an atomelectron arrangement of an atom

Each element has a ground-state Each element has a ground-state electron configurationelectron configuration

Three Rules for Electron Three Rules for Electron ArrangementArrangement

Aufbau PrincipleAufbau Principle Pauli Exclusion PrinciplePauli Exclusion Principle Hund’s RuleHund’s Rule

Aufbau PrincipleAufbau Principle

Each electron occupies the lowest energy Each electron occupies the lowest energy orbital availableorbital available

In order to do this, you must learn the In order to do this, you must learn the sequence of atomic orbitals from lowest to sequence of atomic orbitals from lowest to highest energyhighest energy

Aufbau DiagramAufbau Diagram• Each box represents an orbitalEach box represents an orbital• Each arrow represents an electronEach arrow represents an electron• Only two arrows per box…Only two arrows per box…

Only two electrons per orbitalOnly two electrons per orbital

Some important things to Some important things to remember about Aufbau…remember about Aufbau…

All orbitals related to an energy All orbitals related to an energy sublevel are of equal energysublevel are of equal energy• All three 2p orbitals have the same All three 2p orbitals have the same

energyenergy In a multi-electron atom, the energy In a multi-electron atom, the energy

sublevels within a principle energy sublevels within a principle energy level have different energieslevel have different energies• All three 2p orbitals are of higher energy All three 2p orbitals are of higher energy

than the one 2s orbitalthan the one 2s orbital

In order of increasing energies, the In order of increasing energies, the sequence of energy sublevels within sequence of energy sublevels within a principle energy level is s, p, d, f a principle energy level is s, p, d, f

Orbitals related to energy sublevels Orbitals related to energy sublevels within one principle energy level can within one principle energy level can overlap orbitals related to energy overlap orbitals related to energy sublevels within another principle sublevels within another principle levellevel• Ex. An orbital related to the atoms 4s Ex. An orbital related to the atoms 4s

sublevel has a lower energy than the sublevel has a lower energy than the five orbitals related to 3d sublevel.five orbitals related to 3d sublevel.

Pauli Exclusion PrinciplePauli Exclusion Principle States that a States that a

maximum on 2 maximum on 2 electrons can electrons can occupy a single occupy a single atomic orbital but atomic orbital but only if the only if the electrons have electrons have opposite spinsopposite spins

Wolfgang PauliWolfgang Pauli Austrian PhysicistAustrian Physicist Observed atoms in Observed atoms in

excited statesexcited states

Each electron has a spinEach electron has a spin Kinda like a spinning topKinda like a spinning top It can only spin in one of 2 directionsIt can only spin in one of 2 directions In order for electrons to be together In order for electrons to be together

in an orbital, they must have in an orbital, they must have opposite spinsopposite spins

Hund’s RuleHund’s Rule

What kind of charge do electrons have?What kind of charge do electrons have? Do they attract or repel each other?Do they attract or repel each other? So……..So…….. Hund’s Rule states that single electrons Hund’s Rule states that single electrons

with the same spin must occupy all each with the same spin must occupy all each energy equal orbital before additional energy equal orbital before additional electrons with opposite spins can occupy electrons with opposite spins can occupy the same orbitalthe same orbital

2p orbitals2p orbitals

Read section 5-3!