What is the universe made of…?

•Everything in the universe falls into Everything in the universe falls into two categories: matter, and light!two categories: matter, and light!

•Matter, as we have seen, is made of Matter, as we have seen, is made of atoms, and atoms are made of atoms, and atoms are made of protons, neutrons, and electrons!protons, neutrons, and electrons!

•What is light, though?What is light, though?

•Light is also called energy, which Light is also called energy, which

is also known as electromagnetic is also known as electromagnetic radiation!radiation!

•If you can touch it, it is matter! If you can touch it, it is matter!

Otherwise, it is energy, or light!Otherwise, it is energy, or light!

Light travels in waves….

There are three things we can measure about a light wave - There are three things we can measure about a light wave - Its speed, its frequency, and its wavelength!Its speed, its frequency, and its wavelength!

There are three things we can measure about a light wave - There are three things we can measure about a light wave - Its speed, its frequency, and its wavelength!Its speed, its frequency, and its wavelength!

A

Which wave Which wave

is faster….?is faster….?

A or B…..?A or B…..?

Frequency, Frequency, – number of waves that pass through a particular – number of waves that pass through a particular Point in one second. Units: waves/second, also known as Hertz (Hz)Point in one second. Units: waves/second, also known as Hertz (Hz)Wavelength, Wavelength, - distance between two consecutive waves - - distance between two consecutive waves - Units: meters, mm, cm, nm - any distance units!Units: meters, mm, cm, nm - any distance units!Speed, c - the number of meters a light wave can travel in oneSpeed, c - the number of meters a light wave can travel in onesecond. Units: meters per second (m/s)second. Units: meters per second (m/s)

B

They travel at the same speed!

• They are both light waves, which means that they They are both light waves, which means that they travel at…….travel at…….

• The speed of light!The speed of light!• The speed of light, or c, is equal to 3.00 x 10The speed of light, or c, is equal to 3.00 x 1088 m/s m/s• This is 300 million meters in a second!This is 300 million meters in a second!• That means a light wave can travel around the Earth That means a light wave can travel around the Earth

10 times in a second!10 times in a second!• How do all light waves travel at the same speed?How do all light waves travel at the same speed?

Light and Electromagnetic Radiation

• Electromagnetic radiation, aka energy, Electromagnetic radiation, aka energy,

aka light, includes visible, IR, UV, gamma rays, aka light, includes visible, IR, UV, gamma rays,

X-rays, TV waves, radio waves, and all otherX-rays, TV waves, radio waves, and all other

forms of lightforms of light

• Our eyes are only equipped to see “visible” light, Our eyes are only equipped to see “visible” light,

and all other types of light or energy are and all other types of light or energy are

invisible to us. Our bodies are sensitive to invisible to us. Our bodies are sensitive to

other types of light or energy, though. Which other types of light or energy, though. Which other types of energy can our bodies sense?other types of energy can our bodies sense?

• Pit vipers can see the infrared “color” which Pit vipers can see the infrared “color” which

is radiant heat, a color we cannot see.is radiant heat, a color we cannot see.

• Visible white light is a mixture of all colors in the Visible white light is a mixture of all colors in the

rainbowrainbow

• Speed of light (c) - in a vacuum is constant for Speed of light (c) - in a vacuum is constant for

all types - all types - 3.00 x 103.00 x 1088 m/s m/s

• C = v C = v

High EnergyHigh Energy Low EnergyLow Energy

Light or Electromagnetic Radiation Light or Electromagnetic Radiation or Energyor Energy

• Colors of visible light waves depend on their wavelength or frequencyColors of visible light waves depend on their wavelength or frequency• The different kinds of visible light can be arranged by wavelength into an The different kinds of visible light can be arranged by wavelength into an

electromagnetic spectrumelectromagnetic spectrum• Different colors of visible light have different energies, where violet light Different colors of visible light have different energies, where violet light

has more energy than red light has more energy than red light • Visible light ranges from 400 nm – 800 nmVisible light ranges from 400 nm – 800 nm• ““black light” – which is really near UV light, causes certain objects to black light” – which is really near UV light, causes certain objects to

fluoresce or “glow” fluoresce or “glow” • Fluorescence –UV (non-visible) light is absorbed by electrons in atoms and Fluorescence –UV (non-visible) light is absorbed by electrons in atoms and

then emitted at longer visible wavelengths, such as violet or purple visible then emitted at longer visible wavelengths, such as violet or purple visible lightlight

400 nm

800 nm

Electromagnetic spectrumElectromagnetic spectrum

High EnergyHigh Energy Low EnergyLow Energy

The Electromagnetic SpectrumSmall wavelengthsHigh Frequency(Highest Energy)

Large wavelengthsLow Frequency(Lowest Energy)

So how do matter and energy relate to one another…?

• We know that matter and energy have the ability to interact with one another….

• Matter can absorb energy…..• Examples…?• Matter can give off energy….• Examples…?• And until recently, most people thought that

matter absorbed and released energy continuously….

• What does that mean…?

Think about how things are heated….

• When solids are heated, they emit light of all different energiesWhen solids are heated, they emit light of all different energies• A warm solid at 750A warm solid at 75000C will glow red, and a hot solid at 1000C will glow red, and a hot solid at 100000C C

will glow blue…this makes sense, right? will glow blue…this makes sense, right? • At extremely high temperatures, there were some energies not At extremely high temperatures, there were some energies not

being emitted at all….being emitted at all….• Certain energies in between weren’t emitted as well….Certain energies in between weren’t emitted as well….• This didn’t make sense….This didn’t make sense….• Have you ever seen a pot being heated…?Have you ever seen a pot being heated…?• It gradually heats up….It gradually heats up….• And gradually cools down…!And gradually cools down…!• The energy change is continuous! The energy change is continuous! • It emits all energies, all along the way!It emits all energies, all along the way!

A scientist named Max Planck A scientist named Max Planck studied this intensely!studied this intensely!

• Max Planck was told by his professor not to study physics, as all the Max Planck was told by his professor not to study physics, as all the famous discoveries had been made!famous discoveries had been made!

• He then went on to win the Nobel Prize in 1918!He then went on to win the Nobel Prize in 1918!• Planck’s assumption: vibrating atoms in a heated object gave rise to Planck’s assumption: vibrating atoms in a heated object gave rise to

emitted energy; atoms and molecules could give off or absorb energy only emitted energy; atoms and molecules could give off or absorb energy only in definite amounts, called quanta - not continuously.in definite amounts, called quanta - not continuously.

• He said that energy was not absorbed or given off continuously, but in He said that energy was not absorbed or given off continuously, but in definite amounts….or jumps of energy…..definite amounts….or jumps of energy…..

• This is why, he said, only certain types of energy were seen.This is why, he said, only certain types of energy were seen.• This is called QUANTUM THEORY!This is called QUANTUM THEORY!• Is this what you observe around you?Is this what you observe around you?• This would be the same as driving a car, but only being able to This would be the same as driving a car, but only being able to

drive at 10 mph, and then 20 mph, and then 30 mph, but never drive at 10 mph, and then 20 mph, and then 30 mph, but never in between!in between!

• Does a pot on your stove heat up or cool down like this? Does a pot on your stove heat up or cool down like this? Doesn’t it heat up gradually and cool down gradually?Doesn’t it heat up gradually and cool down gradually?

• How can this be true?How can this be true?• Other scientists thought Max Planck was crazy!Other scientists thought Max Planck was crazy!

Max Planck nearly lost his reputation on Quantum Theory…

• It is obvious that things absorb and release energy continuously….It is obvious that things absorb and release energy continuously….• Think of fires, pots, pans, human bodies, water, etc.Think of fires, pots, pans, human bodies, water, etc.• Experimentally, the quantum assumption part of his theory was Experimentally, the quantum assumption part of his theory was

shaky….shaky….• Even Max Planck tried to eliminate it from his theory!Even Max Planck tried to eliminate it from his theory!• A scientist came along to help him out and save the day by proving A scientist came along to help him out and save the day by proving

him right!him right!• Albert Einstein!Albert Einstein!• He would win his first Nobel Prize for an He would win his first Nobel Prize for an

experiment called the…experiment called the…• Photoelectric Effect!Photoelectric Effect!

Photoelectric Effect Photoelectric Effect Photoelectric Effect Photoelectric Effect

No electrons were emitted untiluntil the frequency of the light was above the frequency of the light was above a minimum frequency, at which point all electrons were emitted from a minimum frequency, at which point all electrons were emitted from the surface! That minimum frequency is different for every substance the surface! That minimum frequency is different for every substance in the universe!in the universe!

No electrons were emitted untiluntil the frequency of the light was above the frequency of the light was above a minimum frequency, at which point all electrons were emitted from a minimum frequency, at which point all electrons were emitted from the surface! That minimum frequency is different for every substance the surface! That minimum frequency is different for every substance in the universe!in the universe!

electrons emitted ?

NoNo

Yes, withYes, with high speed high speed

Trying to increase the energy by increasing the

amount of red light each time

NoNo

NoNo

NoNo

NoNo

SodiumSodium

Blue LightBlue Light

Violet LightViolet Light

Red LightRed Light

ee--

Red LightRed Light

NoNo

ee--

ee--

Changing the color of the light

electrons emitted ?

SodiumSodium

Violet

•If energy absorption was continuous, what should have happened when the amount of red light was increased gradually….?

•Gradually, more and more electrons should have left!

•But nothing happened when the red light amount was increased!

•This told Einstein that energy absorption was not gradual or continuous, but occurred in definite amounts, or quanta

•The real question was this - HOW DID A LIGHT WAVE MOVE MATTER?

•An electron is matter, right?

•Have you ever had a light wave move you? You are made of matter, right?

Photoelectric Effect Photoelectric Effect Photoelectric Effect Photoelectric Effect

Many scientists laughed at Einstein! They said that his idea was ridiculous! It was Many scientists laughed at Einstein! They said that his idea was ridiculous! It was impossible for light to move an electron! Or any matter!impossible for light to move an electron! Or any matter! So Einstein said…..So Einstein said…..LIGHT IS MADE OF MATTER! LIGHT IS MADE OF MATTER! Each light wave contains tiny little particles called photons!Each light wave contains tiny little particles called photons!Not Not protons, protons, but but photons!photons! Increasing the amount of waves is simply increasing the numberIncreasing the amount of waves is simply increasing the numberof photons, but its NOT increasing the energy of each wave!of photons, but its NOT increasing the energy of each wave! However, if the energy of these “photons” is related to their However, if the energy of these “photons” is related to their frequency, this would explain why higher frequency light waves canfrequency, this would explain why higher frequency light waves canknock the electrons out of atoms, but low frequency light waves can’t…knock the electrons out of atoms, but low frequency light waves can’t…High frequency light waves have more photons, that have more energy, to move matter!High frequency light waves have more photons, that have more energy, to move matter!

Photoelectric Effect Photoelectric Effect Photoelectric Effect Photoelectric Effect

“Photon”

Before Collision After Collision

Photoelectric Effect Photoelectric Effect Photoelectric Effect Photoelectric Effect The only way to move matter is WITH matter!The only way to move matter is WITH matter!Why, then, do light waves not move your electrons or atoms?Why, then, do light waves not move your electrons or atoms?They do!They do!Remember, every matter in the universe is sensitive to photons of a particular light!Remember, every matter in the universe is sensitive to photons of a particular light!What kind of light waves can do damage to your atoms?What kind of light waves can do damage to your atoms?UV waves, X Rays, or Gamma Waves can remove electrons from your DNA UV waves, X Rays, or Gamma Waves can remove electrons from your DNA and cause permanent damage to your cells! Visible waves do not have enough photons and cause permanent damage to your cells! Visible waves do not have enough photons to cause damage!to cause damage!In this atomic picture, the energy of the photon must overcome the In this atomic picture, the energy of the photon must overcome the binding energybinding energy of the electron to the nucleus. of the electron to the nucleus. If the energy of the photon exceeds the binding energy, theIf the energy of the photon exceeds the binding energy, theelectron is given off!electron is given off!

The only way to move matter is WITH matter!The only way to move matter is WITH matter!Why, then, do light waves not move your electrons or atoms?Why, then, do light waves not move your electrons or atoms?They do!They do!Remember, every matter in the universe is sensitive to photons of a particular light!Remember, every matter in the universe is sensitive to photons of a particular light!What kind of light waves can do damage to your atoms?What kind of light waves can do damage to your atoms?UV waves, X Rays, or Gamma Waves can remove electrons from your DNA UV waves, X Rays, or Gamma Waves can remove electrons from your DNA and cause permanent damage to your cells! Visible waves do not have enough photons and cause permanent damage to your cells! Visible waves do not have enough photons to cause damage!to cause damage!In this atomic picture, the energy of the photon must overcome the In this atomic picture, the energy of the photon must overcome the binding energybinding energy of the electron to the nucleus. of the electron to the nucleus. If the energy of the photon exceeds the binding energy, theIf the energy of the photon exceeds the binding energy, theelectron is given off!electron is given off!

What does a discussion about light have to do What does a discussion about light have to do with the structure of the atom?with the structure of the atom?

• A scientist named Neils Bohr, a great friend of Einstein, noticed something peculiar A scientist named Neils Bohr, a great friend of Einstein, noticed something peculiar about Hydrogenabout Hydrogen

• A hydrogen atom consists of 1 electron orbiting 1 proton….A hydrogen atom consists of 1 electron orbiting 1 proton….

• As we know, when substances absorb energy, they can release that energy as well!As we know, when substances absorb energy, they can release that energy as well!

• Atoms can release all kinds of different energy - visible light, infrared light (heat), Atoms can release all kinds of different energy - visible light, infrared light (heat), ultraviolet light, etc.ultraviolet light, etc.

• Think about light bulbs, neon lights, fluorescent lights, heat lamps - these are all Think about light bulbs, neon lights, fluorescent lights, heat lamps - these are all examples of how atoms can give off energy!examples of how atoms can give off energy!

• What part of the atom did Bohr now know was responsible for energy absorption, What part of the atom did Bohr now know was responsible for energy absorption, thanks to his good friend Einstein?thanks to his good friend Einstein?

• ……..The electron!..The electron!

• With one electron, how many different types of energy or colors of light do you With one electron, how many different types of energy or colors of light do you think hydrogen can give off….?think hydrogen can give off….?

……. Only one color of light!. Only one color of light!

• Bohr studied a simple experiment, though - one we are going to look at right now!Bohr studied a simple experiment, though - one we are going to look at right now!

• Bohr excited hydrogen atoms with high voltage electricityBohr excited hydrogen atoms with high voltage electricity

• The hydrogen atoms absorbed the electrical energy, and emitted violet lightThe hydrogen atoms absorbed the electrical energy, and emitted violet light

• The violet light was actually FOUR DIFFERENT COLORS OF LIGHT, as The violet light was actually FOUR DIFFERENT COLORS OF LIGHT, as viewed through a prismviewed through a prism

• Each color represents a different wavelength of light!Each color represents a different wavelength of light!

HOW IS THIS POSSIBLE…?HOW IS THIS POSSIBLE…?

• It doesn’t make sense that one electron can be responsible for four It doesn’t make sense that one electron can be responsible for four different colors of light!different colors of light!

• Hydrogen, with only one electron, should be emitting only one type of Hydrogen, with only one electron, should be emitting only one type of energy!energy!

• Bohr came up with an explanation for this….Bohr came up with an explanation for this….

• It involved It involved changingchanging the current accepted model of the atom! the current accepted model of the atom!

• It doesn’t make sense that one electron can be responsible for four It doesn’t make sense that one electron can be responsible for four different colors of light!different colors of light!

• Hydrogen, with only one electron, should be emitting only one type of Hydrogen, with only one electron, should be emitting only one type of energy!energy!

• Bohr came up with an explanation for this….Bohr came up with an explanation for this….

• It involved It involved changingchanging the current accepted model of the atom! the current accepted model of the atom!

Bohr theorized a new model for the Bohr theorized a new model for the atom…atom…

• Bohr suggested that it was possible for electrons to move to many locations or “energy Bohr suggested that it was possible for electrons to move to many locations or “energy levels” within the atom!levels” within the atom!

• This is why he was seeing a line spectra with hydrogen!This is why he was seeing a line spectra with hydrogen!• Bohr used line spectra to explain electron structure in atoms.Bohr used line spectra to explain electron structure in atoms.• The four lines represented something about the one electron in hydrogen moving!The four lines represented something about the one electron in hydrogen moving!• What do you think it represented…?What do you think it represented…?• The electron was moving to more than one location in the atom!The electron was moving to more than one location in the atom!• In Bohr’s Model of the atom, electrons orbit the nucleus like planets orbit the sun.In Bohr’s Model of the atom, electrons orbit the nucleus like planets orbit the sun.• Different distances from the nucleus represent different energiesDifferent distances from the nucleus represent different energies• Electrons can only exist at these specific energy levels, and have specific energies - they Electrons can only exist at these specific energy levels, and have specific energies - they

can never be in between!can never be in between!• This supported Planck’s and Einstein’s “Quantum Theory”!This supported Planck’s and Einstein’s “Quantum Theory”!

•Electrons can absorb a photon of light when Electrons can absorb a photon of light when it collides with the electron – it then moves to it collides with the electron – it then moves to a higher energy level, based on the amount of a higher energy level, based on the amount of light with which it was hitlight with which it was hit

•Electrons can fall to lower energy levels by Electrons can fall to lower energy levels by emitting photons of light equal to the emitting photons of light equal to the difference between the energy level they difference between the energy level they started at and the one they end up atstarted at and the one they end up at

•Ground state – an electron in the lowest Ground state – an electron in the lowest energy level possibleenergy level possible

•Excited state - by absorbing specific energy Excited state - by absorbing specific energy from light, an electron can move to a higher from light, an electron can move to a higher energy level, away from the positive pull of energy level, away from the positive pull of the nucleusthe nucleus

•This excited state is unstable, and the This excited state is unstable, and the electron wants to go back down to its normal electron wants to go back down to its normal ground stateground state

•When the electron falls, it releases light as it When the electron falls, it releases light as it falls back down to the ground statefalls back down to the ground state

•Why, then, does hydrogen give off four Why, then, does hydrogen give off four distinct colors of visible light?distinct colors of visible light?

•

So how did one So how did one electron give off four electron give off four

different colors of different colors of light…?light…?

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Types of light spectraTypes of light spectra

Continuous SpectraContinuous SpectraAll lines of color are All lines of color are continuously emitted continuously emitted (Also known as (Also known as white light)white light)

Continuous SpectraContinuous SpectraAll lines of color are All lines of color are continuously emitted continuously emitted (Also known as (Also known as white light)white light)

Line SpectraLine SpectraOnly certain lines of colorOnly certain lines of colorare seenare seen

Line SpectraLine SpectraOnly certain lines of colorOnly certain lines of colorare seenare seen

Excited Electrons and Spectra

• Line spectra - when light emitted by atoms of an element is passed through a prism, Line spectra - when light emitted by atoms of an element is passed through a prism, only very specific colors come out, and not a rainbowonly very specific colors come out, and not a rainbow

• Elements can be identified by their unique line spectraElements can be identified by their unique line spectra

• Many elements were discovered this way!Many elements were discovered this way!

• Janseen discovered He, by light from sun, in 1868.Janseen discovered He, by light from sun, in 1868.

• Information known about extraterrestrial objects comes from emitted light.Information known about extraterrestrial objects comes from emitted light.

CarbonCarbon

HeliumHelium

NeonNeon

Line Spectra Diagram for HydrogenLine Spectra Diagram for HydrogenLine Spectra Diagram for HydrogenLine Spectra Diagram for Hydrogen

• The lines of light we The lines of light we see correspond to see correspond to electrons moving from electrons moving from one energy level to one energy level to another!another!

• The greater the fall, The greater the fall, the more the energy the more the energy they release!they release!

Electrons in Energy LevelsElectrons in Energy Levels

• The maximum number of electrons in any energy level is = 2n2

• Level 2n2 maximum number of electrons

• 1 2(1)2 2• 2 2(2)2 8• 3 2(3)2 18• 4 2(4)2 32

2e-

n= 1

n= 2

n= 3

18e-

8e-

n= 4

32e-

Now we are done redesigning the atom, right….?

• Wrong!

• 1924 Louis DeBroglie proposed that because light

waves act somewhat like matter, then matter must

act like light waves!

• That means that all matter - ducks, bowling balls, planes, electrons, even you and me - all travel in waves!

• This didn’t make sense, since most people could see that most objects traveled in straight lines! ??

But all matter does travel in waves!

• In 1927, 2 scientists at Bell Laboratories proved that DeBroglie was right!In 1927, 2 scientists at Bell Laboratories proved that DeBroglie was right!

• They took X-Ray Crystallography pictures of atoms, and saw that They took X-Ray Crystallography pictures of atoms, and saw that electrons actually traveled in waves!electrons actually traveled in waves!

This caused the model of the atom to be redesigned even This caused the model of the atom to be redesigned even again!again!

Hydrogen AtomHydrogen Atom

If all matter travels in waves, then why can we not see the wave motion of

normal objects?

If all matter travels in waves, then why can we not see the wave motion of

normal objects?

• If you were to measure the wavelength of a duck, or plane, or bee, you If you were to measure the wavelength of a duck, or plane, or bee, you would see relative to the size of the object, and its wavelength would be would see relative to the size of the object, and its wavelength would be incredibly tiny!incredibly tiny!

• Electrons are so incredibly small already!Electrons are so incredibly small already!

• This means that the wavelength of an electron is relatively large This means that the wavelength of an electron is relatively large compared to its size!compared to its size!

• Its wavelike motion is going to affect the atom and its structure…Its wavelike motion is going to affect the atom and its structure…

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Another problem with the puzzle….

• Werner Heisenberg, a Werner Heisenberg, a famous German scientist, famous German scientist, suggested that it was suggested that it was impossible to know impossible to know exactlyexactly where an electron was at all where an electron was at all times!times!

• To watch an electron orbit To watch an electron orbit the nucleus would require the nucleus would require light!light!

• Shining light on an electron Shining light on an electron might do what….?might do what….?

• Move it!Move it!• And electrons are so small, And electrons are so small,

and move so fast, that we and move so fast, that we would lose where it would go!would lose where it would go!

• The Heisenberg Uncertainty The Heisenberg Uncertainty Principle:Principle: It is impossible to It is impossible to simultaneously know an simultaneously know an electron’s location and speed electron’s location and speed around the nucleus of an around the nucleus of an atom.atom.

Unknown new location

Photon of light

So what does So what does THATTHAT mean??? mean???So what does So what does THATTHAT mean??? mean???

• Electrons travel in waves around the nucleus, and Electrons travel in waves around the nucleus, and we can’t be sure where they are some of the time!we can’t be sure where they are some of the time!

• Erwin Schrodinger used complicated Erwin Schrodinger used complicated mathematics and probability to calculate where mathematics and probability to calculate where electrons were most likely to be located.electrons were most likely to be located.

• This new model, called the Quantum Mechanical This new model, called the Quantum Mechanical Model predicts the probability of where the Model predicts the probability of where the electron is going to be 90% of the time!electron is going to be 90% of the time!

• It is also called the electron cloud model or the It is also called the electron cloud model or the 90% probability model!90% probability model!

• It means that we THINK that the electron is It means that we THINK that the electron is located in some region or “cloud” of space, 90% located in some region or “cloud” of space, 90% of the time! But if we went looking for it by of the time! But if we went looking for it by shining light on it, it might move to some shining light on it, it might move to some unpredictable location!unpredictable location!

•A model where we don’t know where the electron is???A model where we don’t know where the electron is???

•But Schrodinger did calculations to figure out exactly where in But Schrodinger did calculations to figure out exactly where in the energy levels we could probably find the electron….the energy levels we could probably find the electron….

•These locations were called sublevels….These locations were called sublevels….

•Even within these sublevels, Schrodinger figured out what shape Even within these sublevels, Schrodinger figured out what shape an electron would be located in when it moved……called an an electron would be located in when it moved……called an orbital!orbital!

•So remember, electrons don’t travel in nice circular orbits…they So remember, electrons don’t travel in nice circular orbits…they travel in unpredictable, wavelike patterns in a 3-dimensional travel in unpredictable, wavelike patterns in a 3-dimensional area….These areas are called sublevels…..the electron could be area….These areas are called sublevels…..the electron could be there at any time! It would be like taking a snapshot there at any time! It would be like taking a snapshot picture….The orbital is a collection of all of the potential picture….The orbital is a collection of all of the potential snapshots…snapshots…

•A model where we don’t know where the electron is???A model where we don’t know where the electron is???

•But Schrodinger did calculations to figure out exactly where in But Schrodinger did calculations to figure out exactly where in the energy levels we could probably find the electron….the energy levels we could probably find the electron….

•These locations were called sublevels….These locations were called sublevels….

•Even within these sublevels, Schrodinger figured out what shape Even within these sublevels, Schrodinger figured out what shape an electron would be located in when it moved……called an an electron would be located in when it moved……called an orbital!orbital!

•So remember, electrons don’t travel in nice circular orbits…they So remember, electrons don’t travel in nice circular orbits…they travel in unpredictable, wavelike patterns in a 3-dimensional travel in unpredictable, wavelike patterns in a 3-dimensional area….These areas are called sublevels…..the electron could be area….These areas are called sublevels…..the electron could be there at any time! It would be like taking a snapshot there at any time! It would be like taking a snapshot picture….The orbital is a collection of all of the potential picture….The orbital is a collection of all of the potential snapshots…snapshots…

Sounds really vague and inaccurate, huh?Sounds really vague and inaccurate, huh?Sounds really vague and inaccurate, huh?Sounds really vague and inaccurate, huh?

Why do we care about where the Why do we care about where the electrons are so much???electrons are so much???

Why do we care about where the Why do we care about where the electrons are so much???electrons are so much???

• The electrons are the outside part of the atom!

• They are the only part of the atom that can be added or removed!

• They are what make an atom “react”! Where they are has everything to do with how an atom will “react”!

• There isn’t much room in the 1st energy level, so it only has one sublevel, or area that the electron can exist in -

• It is called the “s” sublevel.

• It has one orbital, shaped like a sphere

• Every energy level, in fact, has an “s” sublevel, because it simply

means that the electron is moving in a sphere!

•Each energy level has an “s” sublevelEach energy level has an “s” sublevel

•Each “s” sublevel has only one orbital, shaped as a sphereEach “s” sublevel has only one orbital, shaped as a sphere

•Notice that it looks as if there are hundreds of electrons in Notice that it looks as if there are hundreds of electrons in each “s” sublevel; this is actually only one electron. We are each “s” sublevel; this is actually only one electron. We are looking at the electron in all of its possible locations at once!looking at the electron in all of its possible locations at once!

•Each “s” sublevel, being a small sphere, can only hold 2 Each “s” sublevel, being a small sphere, can only hold 2 electrons, no matter what energy level it is in!electrons, no matter what energy level it is in!

•That means the 1st energy level can only hold 2 electrons That means the 1st energy level can only hold 2 electrons total!total!

•Each energy level has an “s” sublevelEach energy level has an “s” sublevel

•Each “s” sublevel has only one orbital, shaped as a sphereEach “s” sublevel has only one orbital, shaped as a sphere

•Notice that it looks as if there are hundreds of electrons in Notice that it looks as if there are hundreds of electrons in each “s” sublevel; this is actually only one electron. We are each “s” sublevel; this is actually only one electron. We are looking at the electron in all of its possible locations at once!looking at the electron in all of its possible locations at once!

•Each “s” sublevel, being a small sphere, can only hold 2 Each “s” sublevel, being a small sphere, can only hold 2 electrons, no matter what energy level it is in!electrons, no matter what energy level it is in!

•That means the 1st energy level can only hold 2 electrons That means the 1st energy level can only hold 2 electrons total!total!

ee--

ee--

ee--

ee--ee--

ee--

The second energy level is larger, The second energy level is larger, and has more room for electrons!and has more room for electrons!The second energy level is larger, The second energy level is larger, and has more room for electrons!and has more room for electrons!

• The 2nd level has 2 types of sublevels - an “s” and a “p” sublevel

• p sublevels are shaped like dumbbells

• Where the “s” sublevel only had one orbital, the p sublevel has 3 “orbitals” or shapes!

• Each orbital is identical in shape, except for its orientation in space!

• Each orbital in the “p” sublevel can hold a maximum of 2 electrons, so any “p” sublevel can hold a maximum of 6 electrons total!

• Remember - when talking about a “p” sublevel, you aren’t referring to a particular energy level - you are saying something about how an electron moves!

• You are saying it exists in a dumbbell-like space!

Shapes of “p”

Orbitals

Shapes of “p”

Orbitalsee--

ee--

ee--

ee--ee--ee--ee--

ee--

ee--

ee--

ee--

ee--

So how many electrons can the 2nd energy level TOTAL?So how many electrons can the 2nd energy level TOTAL?So how many electrons can the 2nd energy level TOTAL?So how many electrons can the 2nd energy level TOTAL?

•The 2nd energy level has a “s” The 2nd energy level has a “s” sublevel, with 1 orbital, and a “p” sublevel, with 1 orbital, and a “p” sublevel, with 3 orbitalssublevel, with 3 orbitals

•Each orbital can hold 2 eEach orbital can hold 2 e-- maximum!maximum!

•Total of 8 eTotal of 8 e--!!

•The 2nd energy level has a “s” The 2nd energy level has a “s” sublevel, with 1 orbital, and a “p” sublevel, with 1 orbital, and a “p” sublevel, with 3 orbitalssublevel, with 3 orbitals

•Each orbital can hold 2 eEach orbital can hold 2 e-- maximum!maximum!

•Total of 8 eTotal of 8 e--!!

•The 3rd energy level has 3 sublevels - an “s”, a “p”, and a “d” sublevelThe 3rd energy level has 3 sublevels - an “s”, a “p”, and a “d” sublevel

•The “d” sublevel has 5 “orbitals” or shapesThe “d” sublevel has 5 “orbitals” or shapes

•With each holding 2 eWith each holding 2 e--, the “d” sublevel can hold a maximum of 10 e, the “d” sublevel can hold a maximum of 10 e--

•This allows the 3rd energy level total to hold…..This allows the 3rd energy level total to hold…..

•18 e18 e--!!

ee--

ee--

ee--

ee--

ee--

ee-- ee-- ee-- ee--

ee--

•An atom with 3 energy levels can hold a maximum An atom with 3 energy levels can hold a maximum of how many electrons, then?of how many electrons, then?

•28 e28 e--!!

•2 in the first energy level - 2 in the “s” sublevel2 in the first energy level - 2 in the “s” sublevel

•8 in the second energy level - 2 in the “s” sublevel, 8 in the second energy level - 2 in the “s” sublevel, and 6 in the “p” subleveland 6 in the “p” sublevel

•18 in the third energy level - 2 in the “s” sublevel, 18 in the third energy level - 2 in the “s” sublevel, and 6 in the “p” sublevel, and 10 in the “d” subleveland 6 in the “p” sublevel, and 10 in the “d” sublevel

•An atom with 3 energy levels can hold a maximum An atom with 3 energy levels can hold a maximum of how many electrons, then?of how many electrons, then?

•28 e28 e--!!

•2 in the first energy level - 2 in the “s” sublevel2 in the first energy level - 2 in the “s” sublevel

•8 in the second energy level - 2 in the “s” sublevel, 8 in the second energy level - 2 in the “s” sublevel, and 6 in the “p” subleveland 6 in the “p” sublevel

•18 in the third energy level - 2 in the “s” sublevel, 18 in the third energy level - 2 in the “s” sublevel, and 6 in the “p” sublevel, and 10 in the “d” subleveland 6 in the “p” sublevel, and 10 in the “d” sublevel

Some hints….Some hints….

1.1. Any energy level “n” has exactly n sublevels in itAny energy level “n” has exactly n sublevels in it

2.2. Each sublevel has a specific number of orbitals, as seen on the chart belowEach sublevel has a specific number of orbitals, as seen on the chart below

3.3. Since electrons don’t like each other, having the same charge and repelling each other, an orbital can Since electrons don’t like each other, having the same charge and repelling each other, an orbital can

hold a maximum of only 2 ehold a maximum of only 2 e--. This is known as the . This is known as the Pauli Exclusion Principle.Pauli Exclusion Principle.

4.4. Remember - a sublevel simply tells us where an electron is located, and an orbital tells us something Remember - a sublevel simply tells us where an electron is located, and an orbital tells us something

about the shape that it moves within as it travels in a wave!about the shape that it moves within as it travels in a wave!

Some hints….Some hints….

1.1. Any energy level “n” has exactly n sublevels in itAny energy level “n” has exactly n sublevels in it

2.2. Each sublevel has a specific number of orbitals, as seen on the chart belowEach sublevel has a specific number of orbitals, as seen on the chart below

3.3. Since electrons don’t like each other, having the same charge and repelling each other, an orbital can Since electrons don’t like each other, having the same charge and repelling each other, an orbital can

hold a maximum of only 2 ehold a maximum of only 2 e--. This is known as the . This is known as the Pauli Exclusion Principle.Pauli Exclusion Principle.

4.4. Remember - a sublevel simply tells us where an electron is located, and an orbital tells us something Remember - a sublevel simply tells us where an electron is located, and an orbital tells us something

about the shape that it moves within as it travels in a wave!about the shape that it moves within as it travels in a wave!

nn # sublevels# sublevels“names”“names”

11 11 ss

22 22 s, ps, p

33 33 s, p, s, p, dd

44 44 s, p, s, p, d, fd, f

55 44 s, p, s, p, d, fd, f

3

2

1

level

2

6

10

1

3

5

s

p

d

2

6

1

3

s

p

21s

Max no. of e-No. of orbitalsublevel

8

18

105d

147f

63p

21s

Max no. of e-No. of orbitalsublevel

Insert figure 5.31

s, p, d, and f Orbitals

s, p, d, and f Orbitals

Who wants to draw complicated atoms with these sublevels and orbitals included in the picture…?

•Instead, we can use Instead, we can use shorthand for where the shorthand for where the electrons are located!electrons are located!

•There are two shorthand There are two shorthand ways of indicating where ways of indicating where electrons are located:electrons are located:

•Electron Electron ConfigurationsConfigurations

•Orbital DiagramsOrbital Diagrams

•Let’s look at each and Let’s look at each and discuss why we use them!discuss why we use them!

•Instead, we can use Instead, we can use shorthand for where the shorthand for where the electrons are located!electrons are located!

•There are two shorthand There are two shorthand ways of indicating where ways of indicating where electrons are located:electrons are located:

•Electron Electron ConfigurationsConfigurations

•Orbital DiagramsOrbital Diagrams

•Let’s look at each and Let’s look at each and discuss why we use them!discuss why we use them!

Electron Configurations

• We use this shorthand to indicate where electrons live…

• We use numbers to indicate the energy level, letters to indicate the shape or sublevel, and superscripts (exponents) to indicate how many electrons there are in a particular sublevel!

• For example, Lithium would be written as:

• Li = 1s22s1

• Notice there are 3 electrons total - 2 electrons in the s sublevel of the 1st energy level, and 1 electron in the s sublevel of the 2nd energy level!

Li = 1s22s1

energy level sublevel

# of electrons

What energy level would an electron fill first…?

• The lowest possible energy level, of course!The lowest possible energy level, of course!

• Electrons are negative!Electrons are negative!

• They want to be as close to the nucleus as possible!They want to be as close to the nucleus as possible!

• This is the lowest energy, most stable location..This is the lowest energy, most stable location..

• This is known as the This is known as the Aufbau Principle…Aufbau Principle…

• Electrons fill lowest energy levels first!Electrons fill lowest energy levels first!

• Can we write the electron configuration for sodium, then?Can we write the electron configuration for sodium, then?

• Sodium has….Sodium has….

• 11 electrons!11 electrons!

• We know that electrons would first occupy the first energy level!We know that electrons would first occupy the first energy level!

• Once that is filled, they would then fill the second, and then the third, etc.Once that is filled, they would then fill the second, and then the third, etc.

Na = 1sNa = 1s222s2s222p2p663s3s11

Inverted Triangle Apartment Building

Floor = n

Apt = orbital (s, p, d, f)

s = 1 bedroom = 2 e-

p = 3 bedroom = 6 e-

d = 5 bedroom = 10 e-

f = 7 bedroom = 14 e-

(2 e- per room)

Electron ConfigurationsElectron ConfigurationsElectron ConfigurationsElectron Configurations

Notice the Notice the violationviolation of the Aufbau of the Aufbau Principle….Principle….

7s 7p .. .. .. .. ..

6s 6p 6d 6f .. ..

5s 5p 5d 5f ..

4s 4p 4d 4f

3s 3p 3d

2s 2p

1s

Electron ConfigurationsElectron ConfigurationsElectron ConfigurationsElectron Configurations•Look at potassium…

•19 electrons…

•You would think its configuration would be…

•K = 1s22s22p63s23p63d2

•Instead, it is…

•K = 1s22s22p63s23p64s2

•This is known as a violation of the Aufbau Principle!

•Why would an atom DO THIS????

Insert figure 5.36

The second way to show where electrons are located is called an orbital diagram…

• This is a better way of actually seeing where electrons are!This is a better way of actually seeing where electrons are!

• We draw square boxes to indicate sublevels….We draw square boxes to indicate sublevels….

• We draw up and down arrows to indicate electrons…We draw up and down arrows to indicate electrons…

• Oxygen would be written like this….Oxygen would be written like this….

O = O =

•Each box represents a shape - a sphere, a figure 8, etc.Each box represents a shape - a sphere, a figure 8, etc.

•Notice anything weird about this…?Notice anything weird about this…?

•The last two electrons filled separate orbitals first!The last two electrons filled separate orbitals first!

•Why would they fill separate p orbitals first, instead of just Why would they fill separate p orbitals first, instead of just going into the same orbital?going into the same orbital?

•Electrons repel each other, and want to stay as far away from Electrons repel each other, and want to stay as far away from each other as possible!each other as possible!

•This is known as This is known as Hund’s ruleHund’s rule - electrons fill singly occupied - electrons fill singly occupied orbitals first!orbitals first!

An orbital An orbital diagram….diagram….

De Broglie Model!De Broglie Model!

I thank you for your I thank you for your attention! Until the next attention! Until the next model of the atom….!model of the atom….!

I thank you for your I thank you for your attention! Until the next attention! Until the next model of the atom….!model of the atom….!