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Chapter 6Chapter 6Atomic StructureAtomic Structure

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LightLight Made up of electromagnetic Made up of electromagnetic

radiation.radiation. Can behave as a particle as well as a Can behave as a particle as well as a

wavewave

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Parts of a waveParts of a wave

Wavelength

Frequency = number of cycles in one secondMeasured in hertz 1 hertz = 1 cycle/second

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Frequency = Frequency =

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Kinds of EMR waves Kinds of EMR waves There are radio, micro, IR, Vis, UV, X-There are radio, micro, IR, Vis, UV, X-

rays and gamma rays rays and gamma rays Each have different Each have different and and Visible light is only the part our eyes Visible light is only the part our eyes

can detect.can detect.

GammaRays

Radiowaves

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The speed of lightThe speed of light in a vacuum is 2.998 x 10in a vacuum is 2.998 x 1088 m/s m/s Denoted by cDenoted by c c = c = What is the wavelength of light with a What is the wavelength of light with a

frequency 5.89 x 10frequency 5.89 x 1055 Hz? Hz? What is the frequency of blue light What is the frequency of blue light

with a wavelength of 484 nm?with a wavelength of 484 nm?

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In 1900In 1900 Matter and energy were seen as Matter and energy were seen as

different from each other in different from each other in fundamental ways.fundamental ways.

Matter was particles.Matter was particles. Energy could come in waves, with Energy could come in waves, with

any frequency.any frequency. Max Planck found that as the cooling Max Planck found that as the cooling

of hot objects couldn’t be explained of hot objects couldn’t be explained by viewing energy as a wave.by viewing energy as a wave.

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Energy is QuantizedEnergy is Quantized Planck found Planck found E came in chunks with E came in chunks with

size hsize h E = nhE = nh where n is an integer.where n is an integer. and h is Planck’s constant and h is Planck’s constant h = 6.626 x 10h = 6.626 x 10-34-34 J s J s these packets of hthese packets of h are called are called

quantumquantum

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Einstein is nextEinstein is next Said electromagnetic radiation is Said electromagnetic radiation is

quantized in particles called photons.quantized in particles called photons. Each photon has energy (E) = hEach photon has energy (E) = h = =

hc/hc/ Combine this with E = mcCombine this with E = mc22 You get the apparent mass of a You get the apparent mass of a

photon.photon. m = h / (m = h / (c)c)

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Which is it?Which is it? Is energy a wave like light, or a Is energy a wave like light, or a

particle?particle? Yes Yes Concept is called the Wave -Particle Concept is called the Wave -Particle

duality.duality. What about the other way, is matter a What about the other way, is matter a

wave? wave? YesYes

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Matter as a waveMatter as a wave Using the velocity v instead of the Using the velocity v instead of the

wavelength wavelength we get. we get. De Broglie’s equation De Broglie’s equation = h/mv = h/mv Can calculate the wavelength of an Can calculate the wavelength of an

object.object.

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ExamplesExamples The laser light of a CD is 7.80 x 10The laser light of a CD is 7.80 x 1022 m. m.

What is the frequency of this light?What is the frequency of this light? What is the energy of a photon of this What is the energy of a photon of this

light?light? What is the apparent mass of a What is the apparent mass of a

photon of this light?photon of this light? What is the energy of a mole of these What is the energy of a mole of these

photons?photons?

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DiffractionDiffraction When light passes through, or When light passes through, or

reflects off, a series of thinly spaced reflects off, a series of thinly spaced lines, it creates a rainbow effect lines, it creates a rainbow effect

because the waves interfere with because the waves interfere with each other. each other.

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A wave moves toward a slit.

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Comes out as a curve

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What will an electron do?What will an electron do? It has mass, so it is matter.It has mass, so it is matter. A particle can only go through one A particle can only go through one

hole.hole. A wave through many holes.A wave through many holes. An electron makes an interference An electron makes an interference

pattern.pattern. It behaves like a wave.It behaves like a wave. Other matter has wavelengths too Other matter has wavelengths too

small to notice.small to notice.

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SpectrumSpectrum The range of frequencies present in The range of frequencies present in

light.light. White light has a continuous White light has a continuous

spectrum.spectrum. All the colors are possible.All the colors are possible. A rainbow.A rainbow.

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Hydrogen spectrumHydrogen spectrum Emission spectrum because these are the Emission spectrum because these are the

colors it gives off or emits.colors it gives off or emits. Called a line spectrum.Called a line spectrum. There are just a few discrete lines showingThere are just a few discrete lines showing

410 nm

434 nm

486 nm

656 nm

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What this meansWhat this means Only certain energies are absorbed Only certain energies are absorbed

for the hydrogen atom.for the hydrogen atom. So, it can only give off certain So, it can only give off certain

energies.energies. Use Use E = hE = h= hc / = hc / Energy in the atom is quantized. Energy in the atom is quantized.

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Niels BohrNiels Bohr Developed the quantum model of the Developed the quantum model of the

hydrogen atom.hydrogen atom. He said the atom was like a solar He said the atom was like a solar

system.system. The electrons were attracted to the The electrons were attracted to the

nucleus because of opposite nucleus because of opposite charges.charges.

Didn’t fall in to the nucleus because Didn’t fall in to the nucleus because it was moving around.it was moving around.

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The Bohr Ring AtomThe Bohr Ring Atom He didn’t know why but only certain He didn’t know why but only certain

energies were absorbed.energies were absorbed. He called these allowed energies energy He called these allowed energies energy

levels.levels. Putting energy into the atom moved the Putting energy into the atom moved the

electron away from the nucleus.electron away from the nucleus. From its ground state to its excited state.From its ground state to its excited state. When it returns to ground state it gives off When it returns to ground state it gives off

light of a certain energy.light of a certain energy.

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The Bohr Ring AtomThe Bohr Ring Atom

n = 3n = 4

n = 2n = 1

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The Bohr Model EquationThe Bohr Model Equation RRHH Rydberg constant -2.178 x 10 Rydberg constant -2.178 x 10-18-18JJ n is the energy leveln is the energy level E = -2.178 x 10E = -2.178 x 10-18-18 J / nJ / n22 n = 1 is called the ground staten = 1 is called the ground state Used to find the energy of one Used to find the energy of one

hydrogen electronhydrogen electron

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We are worried about the change We are worried about the change When the electron moves from one When the electron moves from one

energy level to another.energy level to another. E = EE = Efinal final - E- Einitialinitial

hv = -2.178 x 10hv = -2.178 x 10-18-18 J x (1/ nJ x (1/ nff22 - 1/ n - 1/ nii

22))

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ExamplesExamples Calculate the energy need to move an Calculate the energy need to move an

electron from its first to third energy electron from its first to third energy levels.levels.

Calculate the frequency released Calculate the frequency released when an electron moves from n= 4 to when an electron moves from n= 4 to n=2 in a hydrogen atom.n=2 in a hydrogen atom.

Calculate the energy released when Calculate the energy released when an electron moves from n= 5 to n=3an electron moves from n= 5 to n=3

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When is it true?When is it true? Only for hydrogen atoms and other Only for hydrogen atoms and other

monoelectronic species (Hemonoelectronic species (He+1+1).). Why the negative sign?Why the negative sign? B/c to increase the energy of the B/c to increase the energy of the

electron you make it closer to the electron you make it closer to the nucleus.nucleus.

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The Bohr ModelThe Bohr Model Doesn’t work.Doesn’t work. Only works for hydrogen atoms.Only works for hydrogen atoms. Electrons don’t move in circles.Electrons don’t move in circles. The quantization of energy is rightThe quantization of energy is right

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The Quantum Mechanical ModelThe Quantum Mechanical Model A totally new approach.A totally new approach. De Broglie said matter could be like a De Broglie said matter could be like a

wave.wave. De Broglie said they were like De Broglie said they were like

standing waves.standing waves. The vibrations of a stringed The vibrations of a stringed

instrument.instrument.

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Schroedinger’s EquationSchroedinger’s Equation The wave is a function of (x, y, z)The wave is a function of (x, y, z) Solutions to the equation are called Solutions to the equation are called

orbitals.orbitals. These are not Bohr orbits.These are not Bohr orbits. Each solution is tied to a certain Each solution is tied to a certain

energy.energy. These are the energy levels.These are the energy levels.

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There is a limit to what we can There is a limit to what we can knowknow

We can’t know how the electron is We can’t know how the electron is moving or how it gets from one moving or how it gets from one energy level to another.energy level to another.

The Heisenberg Uncertainty The Heisenberg Uncertainty Principle.Principle.

There is a limit to how well we can There is a limit to how well we can know both the position and the know both the position and the momentum of an object.momentum of an object.

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What does the wave Function What does the wave Function mean?mean?

nothing.nothing. it is not possible to visually map it.it is not possible to visually map it. The square of the function is the The square of the function is the

probability of finding an electron near a probability of finding an electron near a particular spot.particular spot.

best way to visualize it is by mapping best way to visualize it is by mapping the places where the electron is likely to the places where the electron is likely to be found.be found.

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Prob

abili

ty

Distance from nucleus

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Defining the sizeDefining the size The nodal surface.The nodal surface. The size that encloses 90% to the The size that encloses 90% to the

total electron probability.total electron probability. NOT at a certain distance, but a most NOT at a certain distance, but a most

likely distance.likely distance. For the first solution it is a sphere. For the first solution it is a sphere.

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Quantum NumbersQuantum Numbers There are many solutions to There are many solutions to

Schroedinger’s equationSchroedinger’s equation Each solution can be described with Each solution can be described with

quantum numbers that describe quantum numbers that describe some aspect of the solution.some aspect of the solution.

Principal quantum number (n) size Principal quantum number (n) size and energy of an orbital.and energy of an orbital.

Has integer values >0Has integer values >0

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Quantum numbersQuantum numbers Angular momentum quantum number Angular momentum quantum number ll . . shape of the orbital.shape of the orbital. integer values from 0 to n-1integer values from 0 to n-1 ll = 0 is called s = 0 is called s ll = 1 is called p = 1 is called p ll =2 is called d =2 is called d ll =3 is called f =3 is called f ll =4 is called g =4 is called g

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S orbitals

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P orbitals

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P Orbitals

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D orbitals

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F orbitals

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F orbitals

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Quantum numbersQuantum numbers Magnetic quantum number (mMagnetic quantum number (m ll) ) integer values between - integer values between - ll and + and + ll tells direction of each shapetells direction of each shape Electron spin quantum number (mElectron spin quantum number (m ss) ) Can have 2 values.Can have 2 values. either +1/2 or -1/2either +1/2 or -1/2

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Polyelectronic AtomsPolyelectronic Atoms More than one electron.More than one electron. three energy contributions.three energy contributions. The kinetic energy of moving The kinetic energy of moving

electrons.electrons. The potential energy of the attraction The potential energy of the attraction

between the nucleus and the between the nucleus and the electrons.electrons.

The potential energy from repulsion of The potential energy from repulsion of electrons.electrons.

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The Periodic Table The Periodic Table Developed independently by German Developed independently by German

Meyer and Russian Mendeleev Meyer and Russian Mendeleev (1870’s).(1870’s).

Didn’t know much about atom.Didn’t know much about atom. Put in columns by similar properties.Put in columns by similar properties. Predicted properties of missing Predicted properties of missing

elements.elements.

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Aufbau PrincipleAufbau Principle Aufbau is German for building up.Aufbau is German for building up. As the protons are added one by As the protons are added one by

one, the electrons fill up hydrogen-one, the electrons fill up hydrogen-like orbitals.like orbitals.

Fill up in order of energy levels.Fill up in order of energy levels.

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Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s7s

2p

3p

4p5p6p

3d

4d5d

7p 6d

4f5f

He with 2 electrons

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DetailsDetails Valence electronsValence electrons- the electrons in - the electrons in

the outermost energy levels (not d or the outermost energy levels (not d or f).f).

Core electronsCore electrons- the inner electrons.- the inner electrons. Hund’s RuleHund’s Rule- The lowest energy - The lowest energy

configuration for an atom is the one configuration for an atom is the one that has the maximum number of that has the maximum number of unpaired unpaired electrons in the orbital.electrons in the orbital.

C = 1sC = 1s2 2 2s2s22 2p 2p22

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Fill from the bottom up following Fill from the bottom up following the arrowsthe arrows

1s2s 2p3s 3p 3d4s 4p 4d 4f5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

• 1s2

• 2• electrons

2s2

• 4

2p6 3s2

• 12

3p6 4s2

• 20

3d10 4p6

5s2

• 38

4d10 5p6 6s2

• 56

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DetailsDetails Elements in the same column have the Elements in the same column have the

same electron configuration.same electron configuration. Put in columns because of similar Put in columns because of similar

properties.properties. Similar properties because of electron Similar properties because of electron

configuration.configuration. Noble gases have filled energy levels.Noble gases have filled energy levels. Transition metals are filling the d Transition metals are filling the d

orbitalsorbitals

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ExceptionsExceptions Cr = [Ar] 4sCr = [Ar] 4s11 3d 3d55 Mo as wellMo as well Half filled orbitals.Half filled orbitals. Scientists aren’t sure of why it Scientists aren’t sure of why it

happenshappens same for Cu [Ar] 4ssame for Cu [Ar] 4s11 3d 3d1010 and Ag and Ag

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More exceptionsMore exceptions Lanthanum La: [Xe] 6sLanthanum La: [Xe] 6s22 5d 5d11 Cerium Ce: [Xe] 6sCerium Ce: [Xe] 6s22 4f 4f11 5d 5d11

Promethium Pr: [Xe] 6sPromethium Pr: [Xe] 6s22 4f 4f33 5d 5d00

Gadolinium Gd: [Xe] 6sGadolinium Gd: [Xe] 6s22 4f 4f77 5d 5d11

Lutetium Pr: [Xe] 6sLutetium Pr: [Xe] 6s22 4f 4f1414 5d 5d11

We’ll just pretend that all except Cu We’ll just pretend that all except Cu and Cr follow the rules.and Cr follow the rules.

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Ionization EnergyIonization Energy- The energy - The energy necessary to remove an electron necessary to remove an electron from a gaseous atom.from a gaseous atom.

The ionization energy for a 1s The ionization energy for a 1s electron from sodium is 1.39 x 10electron from sodium is 1.39 x 1055 kJ/mol .kJ/mol .

The ionization energy for a 3s The ionization energy for a 3s electron from sodium is 4.95 x 10electron from sodium is 4.95 x 1022 kJ/mol .kJ/mol .

Demonstrates Demonstrates shielding.shielding.

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ShieldingShielding Electrons on the higher energy levels Electrons on the higher energy levels

tend to be farther out.tend to be farther out. Have to look through the other Have to look through the other

electrons to see the nucleus.electrons to see the nucleus. They are less effected by the nucleus.They are less effected by the nucleus. lower effective nuclear chargelower effective nuclear charge

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Penetration effectPenetration effect The outer energy levels penetrate the The outer energy levels penetrate the

inner levels so the shielding of the inner levels so the shielding of the core electrons is not totally effective.core electrons is not totally effective.

from most penetration to least from most penetration to least penetration the order ispenetration the order is

ns > np > nd > nf (within the same ns > np > nd > nf (within the same energy level).energy level).

This is what gives us our order of This is what gives us our order of filling, electrons prefer s and p. filling, electrons prefer s and p.

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How orbitals differHow orbitals differ The more positive the nucleus, the The more positive the nucleus, the

smaller the orbital.smaller the orbital. A sodium 1s orbital is the same A sodium 1s orbital is the same

shape as a hydrogen 1s orbital, but it shape as a hydrogen 1s orbital, but it is smaller because the electron is is smaller because the electron is more strongly attracted to the more strongly attracted to the nucleus.nucleus.

The helium 1s is smaller as well.The helium 1s is smaller as well. This provides for better shielding.This provides for better shielding.

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Periodic TrendsPeriodic Trends Ionization energy the energy required to Ionization energy the energy required to

remove an electron form a gaseous atomremove an electron form a gaseous atom Highest energy electron removed first. Highest energy electron removed first. First ionization energy (First ionization energy (II11) is that ) is that

required to remove the first electron.required to remove the first electron. Second ionization energy (Second ionization energy (II22) - the ) - the

second electronsecond electron etc. etc.etc. etc.

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Trends in ionization energyTrends in ionization energy for Mg for Mg

• II11 = 735 kJ/mole = 735 kJ/mole• II22 = 1445 kJ/mole = 1445 kJ/mole• II33 = 7730 kJ/mole = 7730 kJ/mole

The effective nuclear charge increases The effective nuclear charge increases as you remove electrons.as you remove electrons.

It takes much more energy to remove a It takes much more energy to remove a core electron than a valence electron core electron than a valence electron because there is less shielding.because there is less shielding.

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Explain this trendExplain this trend For AlFor Al

• II11 = 580 kJ/mole = 580 kJ/mole• II22 = 1815 kJ/mole = 1815 kJ/mole• II33 = 2740 kJ/mole = 2740 kJ/mole• II44 = 11,600 kJ/mole = 11,600 kJ/mole

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Across a PeriodAcross a Period Generally from left to right, Generally from left to right, II11

increases because increases because there is a greater nuclear charge with there is a greater nuclear charge with

the same shielding.the same shielding. As you go down a group As you go down a group II11

decreases because electrons are decreases because electrons are farther away.farther away.

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It is not that simpleIt is not that simple Half filled and filled orbitals are Half filled and filled orbitals are

harder to remove electrons from.harder to remove electrons from. here’s what it looks like on a graph.here’s what it looks like on a graph.

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Firs

t Ion

izat

ion

ener

gy

Atomic number

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Firs

t Ion

izat

ion

ener

gy

Atomic number

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Firs

t Ion

izat

ion

ener

gy

Atomic number

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Atomic and Ionic radiusAtomic and Ionic radius Atomic radius is the relative size of an Atomic radius is the relative size of an

atomatom– Decreases across a periodDecreases across a period– Increases down a groupIncreases down a group

Ionic radius is the relative size of an ionIonic radius is the relative size of an ion– Positive ions get smallerPositive ions get smaller– Negative ions get largerNegative ions get larger– Effective chargeEffective charge

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ElectronegativityElectronegativity Is the tendency of atoms to gain Is the tendency of atoms to gain

electronselectrons Increases acrossIncreases across Decreases downDecreases down Scale of 4.0 (F) – 0.8 (Cs)Scale of 4.0 (F) – 0.8 (Cs)

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Special groupsSpecial groups Group 1 Alkali metalsGroup 1 Alkali metals Group 2 Alkaline earth metalsGroup 2 Alkaline earth metals Group 17 HalogensGroup 17 Halogens Group 18 Noble gasesGroup 18 Noble gases