Waves All waves, whether they are water waves or electromagnetic waves, can be described in terms...

Waves• All waves, whether they are water waves

or electromagnetic waves, can be described in terms of four characteristics:

• amplitude• wavelength• frequency• speed

AmplitudeAmplitude The amplitude of a wave is the The amplitude of a wave is the

height of the wave measured height of the wave measured from the origin to its crest.from the origin to its crest.

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WavelengthWavelength The wavelength of a wave is the The wavelength of a wave is the

distance that the wave travels as distance that the wave travels as it completes one full cycle of it completes one full cycle of upward and downward motion.upward and downward motion.

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Visible Light Visible Light WavelengthsWavelengths Visible light has wavelengths in the Visible light has wavelengths in the

range of 400 to 750 nmrange of 400 to 750 nm

Remember that a nanometer is 10Remember that a nanometer is 10-9-9 metermeter

You may remember the visible light You may remember the visible light spectrum as ROYGBIVspectrum as ROYGBIV

FrequencyFrequency The frequency of a wave tells how The frequency of a wave tells how

fast the wave oscillates up and fast the wave oscillates up and down.down.

The frequency of light is measured The frequency of light is measured by the number of times a light wave by the number of times a light wave completes a cycle of upward and completes a cycle of upward and downward motion in one second.downward motion in one second.

Units can be: cycles/sec or HertzUnits can be: cycles/sec or Hertz

Speed of LightSpeed of Light Light moves through space at a Light moves through space at a

constant speed of 3.00 x 10constant speed of 3.00 x 1088 m/s m/s

You will use c = 3.00 x 10You will use c = 3.00 x 1088 m/s m/s

Wavelength and Wavelength and Frequency CalculationFrequency Calculation λλ = c/v = c/v

If the frequency of radiation is 3 x If the frequency of radiation is 3 x 10101515 cycles/sec, what is the cycles/sec, what is the wavelength?wavelength?

Wavelength and Wavelength and Frequency CalculationFrequency Calculation λλ = c/v = c/v

If the wavelength of radiation is If the wavelength of radiation is 3 x 103 x 10-4-4 m, what is the frequency? m, what is the frequency?

Electromagnetic Electromagnetic SpectrumSpectrum Electromagnetic radiation can be described in Electromagnetic radiation can be described in

terms of a stream of terms of a stream of photonsphotons, which are , which are massless particles each traveling in a wave-like massless particles each traveling in a wave-like pattern and moving at the pattern and moving at the speed of lightspeed of light. Each . Each photon contains a certain amount (or bundle) photon contains a certain amount (or bundle) of energy, and all electromagnetic radiation of energy, and all electromagnetic radiation consists of these photons. The only difference consists of these photons. The only difference between the various types of electromagnetic between the various types of electromagnetic radiation is the amount of energy found in the radiation is the amount of energy found in the photons. Radio waves have photons with low photons. Radio waves have photons with low energies, microwaves have a little more energy energies, microwaves have a little more energy than radio waves, infrared has still more, then than radio waves, infrared has still more, then visible, ultraviolet, X-rays, and ... the most visible, ultraviolet, X-rays, and ... the most energetic of all ... gamma-rays.energetic of all ... gamma-rays.

Electromagnetic Electromagnetic SpectrumSpectrum

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Radio WavesRadio WavesRadioRadio: yes, this is the same kind of energy : yes, this is the same kind of energy

that radio stations emit into the air for that radio stations emit into the air for your boom box to capture and turn into your boom box to capture and turn into your favorite Mozart, Madonna, or Coolio your favorite Mozart, Madonna, or Coolio tunes. But radio waves are also emitted tunes. But radio waves are also emitted by other things ... such as by other things ... such as starsstars and and gases in space. You may not be able to gases in space. You may not be able to dance to what these objects emit, but dance to what these objects emit, but you can use it to learn what they are you can use it to learn what they are made of. made of.

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Radio WavesRadio Waves

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MicrowavesMicrowaves MicrowavesMicrowaves: they will cook your : they will cook your

popcorn in just a few minutes! In popcorn in just a few minutes! In space, microwaves are used by space, microwaves are used by astronomersastronomers to learn about the to learn about the structure of nearby galaxies, structure of nearby galaxies, including our own Milky Way! including our own Milky Way!

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Infrared RadiationInfrared Radiation Infrared: we often think of this as Infrared: we often think of this as

being the same thing as 'heat', being the same thing as 'heat', because it makes our skin feel because it makes our skin feel warm. In space, IR light maps the warm. In space, IR light maps the dustdust between stars. between stars.

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Visible LightVisible Light VisibleVisible: yes, this is the part that : yes, this is the part that

our eyes see. Visible radiation is our eyes see. Visible radiation is emitted by everything from emitted by everything from fireflies to light bulbs to stars ... fireflies to light bulbs to stars ... also by fast-moving particles also by fast-moving particles hitting other particles. hitting other particles.

Don’t All Units Work Don’t All Units Work The Same?The Same? In the older "CGS" version of the In the older "CGS" version of the metricmetric

system, the units used were system, the units used were angstromsangstroms. An . An Angstrom is equal to 0.0000000001 meters Angstrom is equal to 0.0000000001 meters (10-10 m in (10-10 m in scientific notationscientific notation)! In the newer )! In the newer ""SISI" version of the metric system, we think of " version of the metric system, we think of visible light in units of nanometers or visible light in units of nanometers or 0.000000001 meters (10-9 m). In this 0.000000001 meters (10-9 m). In this system, the violet, blue, green, yellow, system, the violet, blue, green, yellow, orange, and red light we know so well has orange, and red light we know so well has wavelengths between 400 and 700 wavelengths between 400 and 700 nanometers. nanometers.

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Visible SpectrumVisible Spectrum

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Ultraviolet RadiationUltraviolet Radiation UltravioletUltraviolet: we know that the Sun is a : we know that the Sun is a

source of ultraviolet (or UV) radiation, source of ultraviolet (or UV) radiation, because it is the UV rays that cause because it is the UV rays that cause our skin to burn! Stars and other "hot" our skin to burn! Stars and other "hot" objects in space emit UV radiation. objects in space emit UV radiation.

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X-ray RadiationX-ray Radiation X-raysX-rays: your doctor uses them to : your doctor uses them to

look at your bones and your look at your bones and your dentist to look at your teeth. Hot dentist to look at your teeth. Hot gases in the gases in the UniverseUniverse also emit X- also emit X-rays . rays .

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Gamma RadiationGamma Radiation Gamma-raysGamma-rays: radioactive materials (some : radioactive materials (some

natural and others made by man in things natural and others made by man in things like nuclear power plants) can emit like nuclear power plants) can emit gamma-rays. Big particle accelerators gamma-rays. Big particle accelerators that scientists use to help them that scientists use to help them understand what understand what mattermatter is made of can is made of can sometimes generate gamma-rays. But the sometimes generate gamma-rays. But the biggest gamma-ray generator of all is the biggest gamma-ray generator of all is the Universe! It makes gamma radiation in all Universe! It makes gamma radiation in all kinds of ways. kinds of ways.

Gamma RadiationGamma Radiation

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Which types of radiation Which types of radiation reach the Earth?reach the Earth?

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What is What is Electromagnetic Electromagnetic Radiation?Radiation? Electromagnetic radiationElectromagnetic radiation from space is unable to reach the from space is unable to reach the

surface of the Earth except at a very few surface of the Earth except at a very few wavelengthswavelengths, such , such as the as the visible spectrumvisible spectrum, radio frequencies, and some , radio frequencies, and some ultraviolet wavelengths. Astronomers can get above enough ultraviolet wavelengths. Astronomers can get above enough of the Earth's atmosphere to observe at some infrared of the Earth's atmosphere to observe at some infrared wavelengths from mountain tops or by flying their wavelengths from mountain tops or by flying their telescopes in an aircraft. Experiments can also be taken up telescopes in an aircraft. Experiments can also be taken up to altitudes as high as 35 km by balloons which can operate to altitudes as high as 35 km by balloons which can operate for months. Rocket flights can take instruments all the way for months. Rocket flights can take instruments all the way above the Earth's atmosphere for just a few minutes before above the Earth's atmosphere for just a few minutes before they fall back to Earth, but a great many important first they fall back to Earth, but a great many important first results in astronomy and astrophysics came from just those results in astronomy and astrophysics came from just those few minutes of observations. For long-term observations, few minutes of observations. For long-term observations, however, it is best to have your detector on an orbiting however, it is best to have your detector on an orbiting satellite ... and get above it all! satellite ... and get above it all!

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Planck’s TheoryPlanck’s Theory Max Planck proposed that there is a Max Planck proposed that there is a

fundamental restriction on the amounts fundamental restriction on the amounts of energy that an object emits or of energy that an object emits or absorbs, and he called each of these absorbs, and he called each of these pieces of energy a quanta.pieces of energy a quanta.

E = hvE = hv Planck’s constant is Planck’s constant is

h= 6.626 x 10h= 6.626 x 10-34-34 Js Js

Planck’s EquationPlanck’s Equation E = hvE = hv

E = amount of energy emitted or E = amount of energy emitted or absorbedabsorbed

h = Planck’s constant 6.626x10h = Planck’s constant 6.626x10-34-34 JsJs

Photoelectric EffectPhotoelectric Effect Einstein used Planck’s equation E=hv Einstein used Planck’s equation E=hv

to explain the photoelectric effect.to explain the photoelectric effect. In the photoelectric effect, electrons In the photoelectric effect, electrons

are ejected from the surface of a metal are ejected from the surface of a metal when light shines on the metalwhen light shines on the metal

Einstein proposed that light consists of Einstein proposed that light consists of quanta of energy that behave like tiny quanta of energy that behave like tiny particles of light.particles of light.

Energy quanta are photons.Energy quanta are photons.

Arthur ComptonArthur Compton Compton demonstrated that a Compton demonstrated that a

photon could collide with an photon could collide with an electron, therefore a photon electron, therefore a photon behaves like a particle.behaves like a particle.

DeBroglieDeBroglie Louis de Broglie determined that Louis de Broglie determined that

particles exhibit wavelike particles exhibit wavelike behavior.behavior.

Dual Nature of LightDual Nature of Light Light acts like particle and Light acts like particle and

behaves like a wave.behaves like a wave.

Types of SpectraTypes of Spectra Continuous Spectrum – a blend of Continuous Spectrum – a blend of

colors one into the other.colors one into the other.

An example of a continuous An example of a continuous spectrum is a rainbow.spectrum is a rainbow.

Types of SpectraTypes of Spectra Emission Spectrum (Bright-line spectrum) Emission Spectrum (Bright-line spectrum)

- a spectrum that contains only certain - a spectrum that contains only certain colors, or wavelengthscolors, or wavelengths

Energy is added to an element sample. Energy is added to an element sample. The electrons absorb the energy and jump The electrons absorb the energy and jump to a higher energy level. They only stay to a higher energy level. They only stay there for an instant and then fall back to a there for an instant and then fall back to a lower energy level. As the electrons fall lower energy level. As the electrons fall back down they emit photons of light. back down they emit photons of light. Each photon has a specific wavelength Each photon has a specific wavelength and frequency.and frequency.

www.cms.k12.nc.us/.../notes/ch04electrons.htmlwww.cms.k12.nc.us/.../notes/ch04electrons.html

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Creating Emission Creating Emission Spectrum LinesSpectrum Lines http://www.800mainstreet.com/spect/emission-flame-exp.htmlhttp://www.800mainstreet.com/spect/emission-flame-exp.html

Helium SpectrumHelium Spectrum

http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/atspect.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/quantum/atspect.html

Colorful ChemicalsColorful Chemicals Try this web site to see the colorful spectra Try this web site to see the colorful spectra

that different metals can create.that different metals can create.

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Bohr’s Model of the Bohr’s Model of the AtomAtom Bohr listened to a lecture by Rutherford (about his model Bohr listened to a lecture by Rutherford (about his model

of the atom). He realized how Planck’s idea of of the atom). He realized how Planck’s idea of quantization could be applied to this model to explain quantization could be applied to this model to explain line spectra.line spectra.

He decided that electrons can be found only in specific He decided that electrons can be found only in specific energy levels with specific amounts of energy.energy levels with specific amounts of energy.

Each energy level was assigned a quantum numberEach energy level was assigned a quantum number

The The ground stateground state is the lowest energy level, n=1, this is the lowest energy level, n=1, this energy level is closest to the nucleusenergy level is closest to the nucleus

Electrons absorb a specific quanta of energy and jump to Electrons absorb a specific quanta of energy and jump to an excited state, n=2 or abovean excited state, n=2 or above

Bohr’s Explanation of Bohr’s Explanation of Hydrogen’s Spectral Hydrogen’s Spectral LinesLines Bohr proposed that when radiation is Bohr proposed that when radiation is

absorbed, an electron jumps from the absorbed, an electron jumps from the ground state to an excited state. ground state to an excited state. Radiation is emitted when the Radiation is emitted when the electron falls back from the higher electron falls back from the higher energy level to a lower one. The energy level to a lower one. The energy of the absorbed or emitted energy of the absorbed or emitted radiation equals the difference radiation equals the difference between the two energy levels between the two energy levels involved. involved.

Bohr’s Explanation of Bohr’s Explanation of Hydrogen’s Spectral Hydrogen’s Spectral Lines ContinuedLines Continued Bohr used his model and Planck’s Bohr used his model and Planck’s

equation, E=hv, to calculate the equation, E=hv, to calculate the frequencies observed in the line frequencies observed in the line spectrum of hydrogen.spectrum of hydrogen.

This model worked well for hydrogen This model worked well for hydrogen with one electron, but not for elements with one electron, but not for elements with larger numbers of electrons.with larger numbers of electrons.

Planck, Einstein and Bohr Planck, Einstein and Bohr described light as consisting of described light as consisting of photons – quanta of energy that photons – quanta of energy that have some of the characteristics have some of the characteristics of particles.of particles.

Heisenberg’s Heisenberg’s Uncertainty PrincipleUncertainty Principle Heisenberg stated that the Heisenberg stated that the

position and the momentum of a position and the momentum of a moving object cannot moving object cannot simultaneously be measured and simultaneously be measured and known exactly.known exactly.

Probability of Locating Probability of Locating an Electron in an Atoman Electron in an Atom think of the electrons as residing think of the electrons as residing

in a cloudin a cloud

more dense areas have a higher more dense areas have a higher probability of finding an electronprobability of finding an electron

Draw a diagram of an atom with a Draw a diagram of an atom with a surrounding electron cloudsurrounding electron cloud

Quantum Mechanical Quantum Mechanical Model of the AtomModel of the Atom

Atomic OrbitalsAtomic Orbitals An atomic orbital is a region An atomic orbital is a region

around the nucleus of an atom around the nucleus of an atom where an electron with a given where an electron with a given energy is likely to be found.energy is likely to be found.

The amount of energy an electron The amount of energy an electron has determines the kind of orbital has determines the kind of orbital it occupies.it occupies.

s sublevels sublevel s orbitals are spherical in shapes orbitals are spherical in shape

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p sublevelsp sublevels p orbitals are dumbbell shapedp orbitals are dumbbell shaped

PPxx P Pyy P Pzz http://www.chemsoc.org/exemplarchem/entries/2004/dublin_fowler/sorbitals.htmlhttp://www.chemsoc.org/exemplarchem/entries/2004/dublin_fowler/sorbitals.html

d sublevelsd sublevels d orbitals can be several shapesd orbitals can be several shapes

ddz2z2 ddx2-y2x2-y2 ddxyxy

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d sublevelsd sublevels

ddxzxz ddyzyz

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f sublevelsf sublevels f orbitals are complicated 3D f orbitals are complicated 3D

shapes shapes that need to be computer that need to be computer generatedgenerated

see see http://nobel.scas.bcit.ca/chem0010http://nobel.scas.bcit.ca/chem0010/unit3/3.3.3_QM_econfig.htm#here/unit3/3.3.3_QM_econfig.htm#here

““To Do” ActivityTo Do” Activity Color the s, p, d, f blocks on the Color the s, p, d, f blocks on the

periodic table.periodic table.

Principal Energy Principal Energy LevelsLevels Principal energy levels in an atom are Principal energy levels in an atom are

designated by the quantum number, n.designated by the quantum number, n.

““n” must be an integern” must be an integer

look at the left hand margin of the look at the left hand margin of the periodic table to find the principal periodic table to find the principal quantum numbersquantum numbers

As “n” increases (i.e. from 1 to 2), the As “n” increases (i.e. from 1 to 2), the electron energy increaseselectron energy increases

SublevelsSublevels Each principal energy level is Each principal energy level is

divided into one or more sublevels.divided into one or more sublevels.

The number of sublevels in each The number of sublevels in each principal energy level equals the principal energy level equals the quantum number, n , for that quantum number, n , for that energy level.energy level.

How do you tell the How do you tell the difference between difference between sublevels?sublevels? Sublevels can be distinguished by Sublevels can be distinguished by

their:their:– shapesshapes– sizessizes– energiesenergies

SublevelsSublevels If “n” = 1If “n” = 1 one sublevelone sublevel “s”“s”

If “n” = 2If “n” = 2 2 sublevels “s” and 2 sublevels “s” and “p”“p”

If “n” = 3If “n” = 3 3 sublevels “s”, “p”, 3 sublevels “s”, “p”, “d”“d”

OrbitalsOrbitals Each sublevel consists of one or Each sublevel consists of one or

more orbitals.more orbitals.

There can never be more than 2 There can never be more than 2 electrons in each orbital.electrons in each orbital.

Electrons in OrbitalsElectrons in Orbitals Electrons behave as if they are Electrons behave as if they are

spinning on their own axis.spinning on their own axis.

A spinning charge creates an A spinning charge creates an electric and magnetic field.electric and magnetic field.

Pauli’s Exclusion Pauli’s Exclusion PrinciplePrinciple 1.1. Each orbital in an atom can Each orbital in an atom can

hold at hold at most 2 electronsmost 2 electrons

2.2. Each of these electrons must Each of these electrons must have have opposite spins.opposite spins.

Electron PairingElectron Pairing Two electrons with opposite spins Two electrons with opposite spins

(in the same orbital) are paired.(in the same orbital) are paired.

Sublevel “s” holds 2 eSublevel “s” holds 2 e Sublevel “p” holds 6 eSublevel “p” holds 6 e Sublevel “d” holds 10 eSublevel “d” holds 10 e Sublevel “f” holds 14 eSublevel “f” holds 14 e

Orbital Diagram “To Orbital Diagram “To Do” ActivityDo” Activity Acquire a clean orbital diagram.Acquire a clean orbital diagram. Only use pencil on your diagram.Only use pencil on your diagram. Use an orbital to build an electron Use an orbital to build an electron

configuration.configuration.

Aufbau PrincipleAufbau Principle Electrons are added one at a time Electrons are added one at a time

to the lowest energy orbitals to the lowest energy orbitals available until all of the electrons available until all of the electrons of the atom have been accounted of the atom have been accounted for.for.

Pauli Exclusion Pauli Exclusion PrinciplePrinciple An orbital can hold up to 2 An orbital can hold up to 2

electronselectrons

Electrons in the same orbital must Electrons in the same orbital must have opposite spinshave opposite spins

Hund’s RuleHund’s Rule Electrons occupy equal energy Electrons occupy equal energy

orbitals so that a maximum orbitals so that a maximum number of unpaired electrons number of unpaired electrons results.results.

This is commonly known as the This is commonly known as the “Seat on the Bus” Rule“Seat on the Bus” Rule