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Chapter 7Chapter 7
Atomic StructureAtomic Structure
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LightLight Made up of electromagnetic radiationMade up of electromagnetic radiation Waves of electric and magnetic fields Waves of electric and magnetic fields
at right angles to each other.at right angles to each other.
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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 EM waves Kinds of EM waves There are many There are many different different and and Radio waves, microwaves, x rays Radio waves, microwaves, x rays
and gamma rays are all examplesand gamma rays are all examples Light is only the part our eyes can Light is only the part our eyes can
detectdetect
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 = c= 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 waysfundamental ways
Matter was particlesMatter was particles Energy could come in waves, with Energy could come in waves, with
any frequency.any frequency. Max Planck found that the cooling of Max Planck found that the cooling of
hot objects couldn’t be explained by hot objects couldn’t be explained by viewing energy as a wave.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 = nhνν 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 hνν are called are called
quantumquantum
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EinsteinEinstein is next is next Said electromagnetic radiation is Said electromagnetic radiation is
quantized in particles called photonsquantized in particles called photons Each photon has energy = hEach photon has energy = hνν = 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
photonphoton 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
frequency frequency νν 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
objectobject
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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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What is the wavelength?What is the wavelength? of an electron with a mass of of an electron with a mass of
9.11 x 109.11 x 10-31-31 kg traveling at kg traveling at 1.0 x 1.0 x
101077 m/s?m/s? Of a softball with a mass of 0.10 kg Of a softball with a mass of 0.10 kg
moving at 125 mi/hr?moving at 125 mi/hr?
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How do they know?How do they know? 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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with two holes
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with two holes Two Curves
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Two Curveswith two holes
Interfere with each other
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Two Curveswith two holes
Interfere with each other
crests add up
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Several waves
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Several wavesSeveral Curves
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Several wavesSeveral waves
Interference Pattern
Several Curves
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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
holehole A wave goes through both holesA wave goes through both holes Light shows Light shows
interference patternsinterference patterns
Electron “gun”
Electron as Particle
Electron “gun”
Electron as wave
Which did it do?
It made the diffraction pattern The electron is a wave Led to Schrödingers equation
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What will an electron do?What will an electron do? An electron does go though both, An electron does go though both,
and makes an interference pattern.and makes an interference pattern. It behaves like a wave.It behaves like a wave. Other matter has wavelengths too Other matter has wavelengths too
short to notice.short to notice.
ImageImage
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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 emitscolors 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
•Spectrum
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What this meansWhat this means Only certain energies are allowed for Only certain energies are allowed for
the hydrogen atom.the hydrogen atom. Can only give off certain energies.Can only give off certain 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
systemsystem 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 aroundit 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 allowed.energies were allowed. He called these allowed energies He called these allowed energies
energy levels.energy levels. Putting energy into the atom moved Putting energy into the atom moved
the electron away from the nucleusthe electron away from the nucleus From ground state to excited state.From ground state to excited state. When it returns to ground state it When it returns to ground state it
gives off light of a certain energygives off 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 ModelThe Bohr Model n is the energy leveln is the energy level for each energy level the energy isfor each energy level the energy is Z is the nuclear charge, which is +1 Z is the nuclear charge, which is +1
for hydrogen.for hydrogen. E = -2.178 x 10E = -2.178 x 10-18-18 J (ZJ (Z22 / n / n22 ) ) n = 1 is called the ground staten = 1 is called the ground state
when the electron is removed, n = when the electron is removed, n = E = 0E = 0
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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
E = -2.178 x 10E = -2.178 x 10-18-18 J ZJ Z22 (1/ n (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 to the third energy electron from its to the third energy level.level.
Calculate the energy released when Calculate the energy released when an electron moves from n= 4 to n=2 in an electron moves from n= 4 to n=2 in a hydrogen atom.a hydrogen atom.
Calculate the energy released when Calculate the energy released when an electron moves from n= 5 to n=3 in an electron moves from n= 5 to n=3 in a Hea He+1+1 ion ion
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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.monoelectronic species. Why the negative sign?Why the negative sign? To increase the energy of the To increase the energy of the
electron you make it further to the electron you make it further to the nucleus.nucleus.
the maximum energy an electron can the maximum energy an electron can have is zero, at an infinite distance. have is zero, at an infinite distance.
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The Bohr ModelThe Bohr Model Doesn’t workDoesn’t work only works for hydrogen atomsonly works for hydrogen atoms electrons don’t move in circleselectrons don’t move in circles the quantization of energy is right, the quantization of energy is right,
but not because they are circling like but not because they are circling like planets.planets.
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The Quantum Mechanical ModelThe Quantum Mechanical Model A totally new approachA 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
instrumentinstrument
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What’s possible?What’s possible? You can only have a standing wave if You can only have a standing wave if
you have complete waves.you have complete waves. There are only certain allowed waves.There are only certain allowed waves. In the atom there are certain allowed In the atom there are certain allowed
waves called electrons.waves called electrons. 1925 Erwin Schroedinger described 1925 Erwin Schroedinger described
the wave function of the electronthe wave function of the electron Much math, but what is important are Much math, but what is important are
the solutionsthe solutions
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SchrSchröödinger’s Equationdinger’s Equation The wave function is a F(x, y, z)The wave function is a F(x, y, z) Actually F(r,Actually F(r,θθ,,φφ)) 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 levelsThese are the energy levels
•Animation
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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 The Heisenberg Uncertainty PrincipleHeisenberg Uncertainty 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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MathematicallyMathematically x · x · (mv) > h/4(mv) > h/4 x is the uncertainty in the positionx is the uncertainty in the position (mv) is the uncertainty in the (mv) is the uncertainty in the
momentum.momentum. the minimum uncertainty is h/4the minimum uncertainty is h/4
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ExamplesExamples What is the uncertainty in the What is the uncertainty in the
position of an electron. mass 9.31 x position of an electron. mass 9.31 x 1010--3131 kg with an uncertainty in the kg with an uncertainty in the speed of 0.100 m/sspeed of 0.100 m/s
What is the uncertainty in the What is the uncertainty in the position of a baseball, mass 0.145 kg position of a baseball, mass 0.145 kg with an uncertainty in the speed of with an uncertainty in the speed of 0.100 m/s0.100 m/s
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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 probability of finding an electron near a particular spot.a 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 the places where the electron is likely to be found.to be found.
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Pro
babi
lity
Distance from nucleus
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Sum
of
all P
roba
bili
ties
Sum
of
all P
roba
bili
ties
Distance from nucleusDistance 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 a sphere. For the first solution it is a a sphere.
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Quantum NumbersQuantum Numbers There are many solutions to There are many solutions to
SchrSchröödinger’s equationdinger’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 orbitaland 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 l l shape of the orbitalshape 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 l l = 1 is called p= 1 is called p l l =2 is called d=2 is called d ll =3 is called f =3 is called f l l =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 in each shape tells direction in 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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1.1. AA2.2. BB3.3. CC4.4. AA5.5. BB6.6. AA7.7. BB8.8. AA9.9. AA
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Polyelectronic AtomsPolyelectronic Atoms More than one electronMore than one electron three energy contributionsthree energy contributions The kinetic energy of moving electronsThe kinetic energy of moving 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 electronselectrons
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Polyelectronic atomsPolyelectronic atoms Can’t solve SchrCan’t solve Schröödinger’s equation dinger’s equation
exactlyexactly Difficulty is repulsion of other Difficulty is repulsion of other
electrons.electrons. Solution is to treat each electron as if it Solution is to treat each electron as if it
were effected by the net field of charge were effected by the net field of charge from the attraction of the nucleus and from the attraction of the nucleus and the repulsion of the electrons.the repulsion of the electrons.
Effective nuclear chargeEffective nuclear charge
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+11
11 electrons
e-Zeff
Sodium Atom
+11 10 otherelectrons
e-
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Effective Nuclear charge Effective Nuclear charge Can be calculated fromCan be calculated from E E
= -2.178 x 10= -2.178 x 10-18-18 J (ZJ (Zeffeff22 / n / n22 ) )
andand
E = -2.178 x 10E = -2.178 x 10-18-18 J ZJ Zeffeff22 (1/ n (1/ nff
22 - 1/ n - 1/ nii22))
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The Periodic Table The Periodic Table Developed independently by German Developed independently by German
Julius Lothar Meyer and Russian Julius Lothar Meyer and Russian Dmitri Mendeleev (1870”s)Dmitri Mendeleev (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 upAufbau 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 energyFill up in order of energy
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Incr
easi
ng e
nerg
y
1s
2s
3s
4s
5s6s7s
2p
3p
4p
5p6p
3d
4d
5d
7p6d
4f
5f6f
Orbitals available to a Hydrogen atom
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Incr
easi
ng e
nerg
y
1s
2s
3s
4s
5s6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
With more electrons, repulsion changes the energy of the orbitals.
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Incr
easi
ng e
nerg
y
1s
2s
3s
4s
5s6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
He with 2 electrons
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Incr
easi
ng e
nerg
y
1s
2s
3s
4s
5s6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
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DetailsDetails Valence electronsValence electrons- the electrons in - the electrons in
the outermost energy levels (not d).the outermost energy levels (not d). 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 have the maximum number of have 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 4f
5s 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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The ShorthandThe Shorthand Write the symbol of the noble gas Write the symbol of the noble gas
before the element before the element Then the rest of the electrons.Then the rest of the electrons. Aluminum - full configurationAluminum - full configuration 1s1s222s2s222p2p663s3s223p3p11
Ne is 1sNe is 1s222s2s222p2p66
so Al is [Ne] 3sso Al is [Ne] 3s223p3p11
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The ShorthandThe Shorthand
Sn- 50 electrons
The noble gas before it is Kr
[ Kr ]
Takes care of 36
Next 5s2
5s2Then 4d10
4d10Finally 5p2 5p2
[ Kr ] 5s24d10 5p2
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ExceptionsExceptions Ti = [Ar] 4sTi = [Ar] 4s22 3d 3d22 V = [Ar] 4sV = [Ar] 4s22 3d 3d33
Cr = [Ar] 4sCr = [Ar] 4s11 3d 3d5 5
Mn = [Ar] 4sMn = [Ar] 4s22 3d 3d55
Half filled orbitals Half filled orbitals Scientists aren’t certain why it Scientists aren’t certain why it
happenshappens same for Cu [Ar] 3dsame for Cu [Ar] 3d1010 4s 4s11
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More exceptionsMore exceptions Lanthanum La: [Xe] 5dLanthanum La: [Xe] 5d11 6s 6s22
Cerium Ce: [Xe] 5dCerium Ce: [Xe] 5d11 4f 4f116s6s22
Promethium Pr: [Xe] 4fPromethium Pr: [Xe] 4f33 6s 6s22
Gadolinium Gd: [Xe] 4fGadolinium Gd: [Xe] 4f77 5d 5d1 1 6s6s22
Lutetium Pr: [Xe] 4fLutetium Pr: [Xe] 4f1414 5d 5d1 1 6s6s22 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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More PolyelectronicMore Polyelectronic We can use ZWe can use Zeffeff to predict properties, to predict properties,
if we determine it’s pattern on the if we determine it’s pattern on the periodic table.periodic table.
Can use the amount of energy it Can use the amount of energy it takes to remove an electron for this.takes to remove an electron for this.
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.
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Remember thisRemember this E = -2.18 x 10E = -2.18 x 10-18 -18 J(ZJ(Z22/n/n22)) was true for Bohr atom.was true for Bohr atom. Can be derived from quantum Can be derived from quantum
mechanical model as wellmechanical model as well for a mole of electrons being removed for a mole of electrons being removed E =(6.02 x 10E =(6.02 x 102323/mol)2.18 x 10/mol)2.18 x 10-18 -18 J(ZJ(Z22/n/n22)) E= 1.13 x 10E= 1.13 x 1066
J/mol(ZJ/mol(Z22/n/n22))
E= 1310 kJ/mol(ZE= 1310 kJ/mol(Z22/n/n22))
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Example Example Calculate the ionization energy of BCalculate the ionization energy of B+4+4
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Remember our simplified atomRemember our simplified atom
+11
11 e-
Zeff
1 e-
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This gives usThis gives us Ionization energy = Ionization energy =
1310 kJ/mol(Z1310 kJ/mol(Zeffeff22/n/n22))
So we can measure ZSo we can measure Zeffeff
The ionization energy for a 1s electron The ionization energy for a 1s electron from sodium is 1.39 x 10from sodium is 1.39 x 1055 kJ/mol . kJ/mol .
The ionization energy for a 3s electron The ionization energy for a 3s electron from sodium is 4.95 x 10from sodium is 4.95 x 1022 kJ/mol . kJ/mol .
Demonstrates Demonstrates shieldingshielding
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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 electrons Have to look through the other electrons
to see the nucleus.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 If shielding were completely effective, ZIf shielding were completely effective, Zeffeff
= 1= 1 Why isn’t it?Why isn’t it?
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PenetrationPenetration There are levels to the electron There are levels to the electron
distribution for each orbitaldistribution for each orbital
2s
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GraphicallyGraphically
Penetration
2s
Rad
ial P
roba
bili
ty
Distance from nucleus
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GraphicallyGraphicallyR
adia
l Pro
babi
lity
Distance from nucleus
3s
87
Rad
ial P
roba
bili
ty
Distance from nucleus
3p
88
Rad
ial P
roba
bili
ty
Distance from nucleus
3d
89
Rad
ial P
roba
bili
ty
Distance from nucleus
4s
3d
90
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 wellThe helium 1s is smaller as well This provides for better shieldingThis provides for better shielding
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Zef
f
1
2
4
5
1Atomic Number
93
Zef
f
1
2
4
5
1
If shielding is perfect Z= 1
Atomic Number
94
Zef
f
1
2
4
5
1
No
shie
ldin
gZ
= Z ef
f
Atomic Number
95
Zef
f
1
2
4
5
16Atomic Number
96
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.
97
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 as The effective nuclear charge increases as
you remove electrons.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 shieldingbecause there is less shielding
98
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 further away and there is more further away and there is more shieldingshielding
100
It is not that simpleIt is not that simple ZZeffeff changes as you go across a changes as you go across a
period, so will period, so will II11
Half-filled and filled orbitals are Half-filled and filled orbitals are harder to remove electrons fromharder to remove electrons from
here’s what it looks likehere’s what it looks like
101
Firs
t Ion
izat
ion
ener
gy
Atomic number
102
Firs
t Ion
izat
ion
ener
gy
Atomic number
103
Firs
t Ion
izat
ion
ener
gy
Atomic number
104
Atomic SizeAtomic Size First problem where do you start First problem where do you start
measuringmeasuring The electron cloud doesn’t have a The electron cloud doesn’t have a
definite edge.definite edge. They get around this by measuring They get around this by measuring
more than 1 atom at a timemore than 1 atom at a time
105
Atomic SizeAtomic Size
Atomic Radius = half the distance between Atomic Radius = half the distance between two nuclei of a diatomic moleculetwo nuclei of a diatomic molecule
}Radius
106
Trends in Atomic Size Trends in Atomic Size Influenced by two factorsInfluenced by two factors ShieldingShielding More shielding is further awayMore shielding is further away Charge on nucleusCharge on nucleus More charge pulls electrons in More charge pulls electrons in
closercloser
107
Group trendsGroup trends As we go down a As we go down a
groupgroup Each atom has Each atom has
another energy another energy levellevel
So the atoms get So the atoms get biggerbigger
HLi
Na
K
Rb
108
Periodic TrendsPeriodic Trends As you go across a period the radius As you go across a period the radius
gets smaller.gets smaller. Same energy levelSame energy level More nuclear chargeMore nuclear charge Outermost electrons are closerOutermost electrons are closer
Na Mg Al Si P S Cl Ar
109
OverallOverall
Atomic Number
Ato
mic
Rad
ius
(nm
)
H
Li
Ne
Ar
10
Na
K
Kr
Rb
110
Electron AffinityElectron Affinity The energy change associated with adding The energy change associated with adding
an electron to a gaseous atoman electron to a gaseous atom High electron affinity gives you energy- High electron affinity gives you energy- exothermicexothermic More negative More negative Increase (more - ) from left to right Increase (more - ) from left to right
– greater nuclear charge.greater nuclear charge. Decrease as we go down a groupDecrease as we go down a group
– More shieldingMore shielding
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Ionic SizeIonic Size Cations form by losing electronsCations form by losing electrons Cations are smaller than the atom Cations are smaller than the atom
they come fromthey come from Metals form cationsMetals form cations Cations of representative elements Cations of representative elements
have noble gas configuration.have noble gas configuration.
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Ionic sizeIonic size Anions form by gaining electronsAnions form by gaining electrons Anions are bigger than the atom they Anions are bigger than the atom they
come fromcome from Nonmetals form anionsNonmetals form anions Anions of representative elements Anions of representative elements
have noble gas configuration.have noble gas configuration.
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Configuration of IonsConfiguration of Ions Ions always have noble gas Ions always have noble gas
configurationconfiguration Na is 1sNa is 1s222s2s222p2p663s3s11 Forms a 1+ ion - 1sForms a 1+ ion - 1s222s2s222p2p66 Same configuration as neonSame configuration as neon Metals form ions with the Metals form ions with the
configuration of the noble gas before configuration of the noble gas before them - they lose electronsthem - they lose electrons
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Configuration of IonsConfiguration of Ions Non-metals form ions by gaining Non-metals form ions by gaining
electrons to achieve noble gas electrons to achieve noble gas configuration.configuration.
They end up with the configuration They end up with the configuration of the noble gas after them.of the noble gas after them.
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Group trendsGroup trends Adding energy levelAdding energy level Ions get bigger as Ions get bigger as
you go downyou go downLi+1
Na+1
K+1
Rb+1
Cs+1
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Periodic TrendsPeriodic Trends Across the period nuclear charge Across the period nuclear charge
increases so they get smaller.increases so they get smaller. Energy level changes between Energy level changes between
anions and cationsanions and cations
Li+1
Be+2
B+3
C+4
N-3O-2 F-1
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Size of Isoelectronic ionsSize of Isoelectronic ions Iso - sameIso - same Iso electronic ions have the same # Iso electronic ions have the same #
of electronsof electrons AlAl+3+3 Mg Mg+2 +2 NaNa+1 +1 Ne FNe F-1 -1 OO-2 -2 and Nand N-3-3 all have 10 electronsall have 10 electrons all have the configuration 1sall have the configuration 1s222s2s222p2p66
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Size of Isoelectronic ionsSize of Isoelectronic ions Positive ions have more protons so Positive ions have more protons so
they are smallerthey are smaller
Al+3
Mg+2
Na+1 Ne F-1 O-2 N-3
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ElectronegativityElectronegativity
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ElectronegativityElectronegativity The tendency for an atom to attract The tendency for an atom to attract
electrons to itself when it is electrons to itself when it is chemically combined with another chemically combined with another element.element.
How “greedy”How “greedy” Big electronegativity means it pulls Big electronegativity means it pulls
the electron toward itself.the electron toward itself. Atoms with large negative electron Atoms with large negative electron
affinity have larger electronegativity.affinity have larger electronegativity.
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Group TrendGroup Trend The further down a group more The further down a group more
shieldingshielding Less attracted (ZLess attracted (Zeffeff)) Low electronegativity.Low electronegativity.
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Periodic TrendPeriodic Trend Metals are at the left endMetals are at the left end Low ionization energy- low effective Low ionization energy- low effective
nuclear chargenuclear charge Low electronegativityLow electronegativity At the right end are the nonmetalsAt the right end are the nonmetals More negative electron affinityMore negative electron affinity High electronegativityHigh electronegativity Except noble gasesExcept noble gases
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Ionization energy, electronegativity
Electron affinity INCREASE
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Atomic size increases,
Ionic size increases
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Parts of the Periodic TableParts of the Periodic Table
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The information it hidesThe information it hides Know the special groupsKnow the special groups It is the number and type of valence It is the number and type of valence
electrons that determine an atom’s electrons that determine an atom’s chemistry.chemistry.
You can get the electron configuration You can get the electron configuration from it.from it.
Metals lose electrons have the lowest IEMetals lose electrons have the lowest IE Non metals- gain electrons most negative Non metals- gain electrons most negative
electron affinitieselectron affinities
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The Alkali MetalsThe Alkali Metals Doesn’t include hydrogen- it behaves Doesn’t include hydrogen- it behaves
as a non-metalas a non-metal decrease in IEdecrease in IE increase in radiusincrease in radius Decrease in densityDecrease in density decrease in melting pointdecrease in melting point Behave as reducing agentsBehave as reducing agents
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Reducing abilityReducing ability Lower IE< better reducing agentsLower IE< better reducing agents Cs>Rb>K>Na>LiCs>Rb>K>Na>Li works for solids, but not in aqueous works for solids, but not in aqueous
solutions.solutions. In solution Li>K>NaIn solution Li>K>Na Why?Why? It’s the water -there is an energy It’s the water -there is an energy
change associated with dissolvingchange associated with dissolving
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Hydration EnergyHydration Energy LiLi++(g) (g) → Li→ Li++(aq)(aq) is exothermic is exothermic for Lifor Li++ -510 kJ/mol -510 kJ/mol for Nafor Na+ + -402 kJ/mol-402 kJ/mol for Kfor K++ -314 kJ/mol -314 kJ/mol Li is so big because of it has a high Li is so big because of it has a high
charge density, a lot of charge on a charge density, a lot of charge on a small atom.small atom.
Li loses its electron more easily Li loses its electron more easily because of this in aqueous solutionsbecause of this in aqueous solutions
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The reaction with waterThe reaction with water Na and K react explosively with waterNa and K react explosively with water Li doesn’t.Li doesn’t. Even though the reaction of Li has a Even though the reaction of Li has a
more negative more negative H than that of Na and KH than that of Na and K Na and K meltNa and K melt H does not tell you speed of reactionH does not tell you speed of reaction More in Chapter 12.More in Chapter 12.
