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Chapter 7Chapter 7

Atomic Atomic StructureStructure

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7.1 Types of EM waves 7.1 Types of EM waves They have different They have different and and Radio waves, microwaves, infra Radio waves, microwaves, infra red, ultraviolet, x-rays and red, ultraviolet, x-rays and gamma rays are all examples.gamma rays are all examples.

Light is only the part our Light is only the part our eyes can detect.eyes can detect.

GammaRays

Radiowaves

Frequency decreases

Wavelength increases

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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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The speed of lightThe speed of light c = in a vacuum is 2.998 x 10c = in a vacuum is 2.998 x 1088 m/s m/s c = c =

What is the wavelength of light What is the wavelength of light with a frequency 5.89 x 10with a frequency 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?

(YDVD) EMwave(YDVD) EMwave

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7.2 Nature of Matter7.2 Nature of Matter 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 Max Planck found that as the cooling of hot objects couldn’t be cooling of hot objects couldn’t be explained by viewing energy as a explained by viewing energy as a wave.wave.

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

E = nE = nhh where n is an integer.where n is an integer. and and hh is Planck’s constant is Planck’s constant hh = 6.626 x 10 = 6.626 x 10-34-34 J•s J•s These packets of These packets of hh are called are called quantum.quantum.

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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 = Each photon has energy = hh = = hhc/c/ Blue color in fireworks has a Blue color in fireworks has a wavelength of 450 nm. How much energy wavelength of 450 nm. How much energy does a photon of blue light have? A does a photon of blue light have? A mole of these photons?mole of these photons?

Combine this with E = mcCombine this with E = mc22 You get the apparent mass of a photon.You get the apparent mass of a photon. m = m = hh/(/(c)c)

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

Yes Yes Concept is called the Wave - Concept is called the Wave - Particle duality. (Flatman)Particle duality. (Flatman)

What about the other way, is What about the other way, is matter a wave? Yesmatter a wave? Yes

Photoelectric Effect Photoelectric Effect (YDVD)(YDVD)

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Matter as a waveMatter as a wave All matter exhibits both particle and All matter exhibits both particle and wave properties.wave properties.

De Broglie’s equation De Broglie’s equation = h/mv = h/mv We can calculate the wavelength of an We can calculate the wavelength of an object.object.

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 photon of What is the apparent mass of a photon of this light?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 What is the wavelength?wavelength? m = m = hh/(/(c) c)

Of an electron with a mass of Of an electron with a mass of

9.11 x 10 9.11 x 10-31-31 kg kg

traveling at 1.0 x 10traveling at 1.0 x 1077 m/s?m/s? Of a softball with a mass of Of a softball with a mass of 0.10 kg moving at 35 mi/hr?0.10 kg moving at 35 mi/hr?

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7.3 Hydrogen spectrum7.3 Hydrogen 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 There are just a few discrete lines showing only certain energies are showing only certain energies are possible.possible.

410 nm

434 nm

486 nm

656 nm

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What this meansWhat this means Only certain energies are Only certain energies are allowed for the hydrogen allowed for the hydrogen atom.atom.

Can only give off certain Can only give off certain energies.energies.

Use Use E = E = hh = = hhc/c/ Energy in the in the atom is Energy in the in the atom is quantized.quantized.

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7.4 Niels Bohr7.4 Niels Bohr Developed the quantum model Developed the quantum model of the hydrogen atom.of the hydrogen atom.

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

The electrons were attracted The electrons were attracted to the nucleus because of to the nucleus because of opposite charges.opposite charges.

Didn’t fall in to the nucleus Didn’t fall in to the nucleus because it was moving around.because 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 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 nucleus.the 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 gives off light of a certain energy.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 level (an integer).n is the energy level (an integer). 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 state.n = 1 is called the ground state. When the electron moves from one energy When the electron moves from one energy level to another.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/ - 1/

nnii22))

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ExamplesExamples E = -2.178 x 10E = -2.178 x 10-18-18J ZJ Z22 (1/ n (1/ nff

22 - 1/ - 1/

nnii22) )

Calculate the energy need to move an Calculate the energy need to move an electron from level n=1 to level n=2.electron from level n=1 to level n=2.

What is the wavelength of light that What is the wavelength of light that must be absorbed by a hydrogen atom in must be absorbed by a hydrogen atom in its ground state to reach this excited its ground state to reach this excited state.state.

Calculate the energy released when an Calculate the energy released when an electron moves from n= 5 to n=3 in a electron moves from n= 5 to n=3 in a HeHe+1+1 ion ion

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The Bohr ModelThe Bohr Model Doesn’t work.Doesn’t work. Only works for hydrogen Only works for hydrogen atoms.atoms.

Electrons don’t move in Electrons don’t move in circles.circles.

The quantization of energy is The quantization of energy is right, but not because they right, but not because they are circling like planets.are circling like planets.

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7.5 The Quantum Mechanical 7.5 The Quantum Mechanical ModelModel A totally new approach.A totally new approach.

De Broglie said matter could De Broglie said matter could be like a wave.be like a wave.

De Broglie said they were De Broglie said they were like standing waves.like standing waves.

The vibrations of a stringed The vibrations of a stringed instrument.instrument.

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What’s possible?What’s possible? You can only have a standing wave You can only have a standing wave if you have complete waves.if you have complete waves.

There are only certain allowed There are only certain allowed waves.waves.

In the atom there are certain In the atom there are certain allowed waves called electrons.allowed waves called electrons.

1925 Erwin Schroedinger described 1925 Erwin Schroedinger described the wave function of the the wave function of the electron.electron.

A lot of math, but what is A lot of math, but what is important are the solutions.important are the solutions.

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Schroedinger’s Schroedinger’s EquationEquation The wave function (The wave function ( is a is a

(x, y, z) function.(x, y, z) function. Solutions to the equation are Solutions to the equation are called orbitals.called orbitals.

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

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

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The Heisenberg The Heisenberg Uncertainty Principle.Uncertainty Principle.

There is a fundamental limitation on There is a fundamental limitation on how precisely we can know both the how precisely we can know both the position and momentum of a particle at position and momentum of a particle at a given time.a given time.

MATHEMATICALLY:MATHEMATICALLY: x · x · (mv) (mv) >> hh/4/4 x is the uncertainty in the position.x is the uncertainty in the position. (mv) is the uncertainty in the (mv) is the uncertainty in the momentum.momentum.

the minimum uncertainty is the minimum uncertainty is hh/4/4

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

Nothing. It is not possible to Nothing. It is not possible to visually map it.visually map it.

The square of the function is The square of the function is the probability of finding an the probability of finding an electron near a particular spot.electron near a particular spot.

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

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

NOT at a certain distance, NOT at a certain distance, but a most likely distance.but a most likely distance.

For the first solution it is For the first solution it is a a sphere.a a sphere. This is of course This is of course and s orbital.and s orbital.

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7.6 Quantum Numbers7.6 Quantum Numbers There are many solutions to There are many solutions to Schroedinger’s equationSchroedinger’s equation

Each solution can be described Each solution can be described with quantum numbers that with quantum numbers that describe some aspect of the describe some aspect of the solution.solution.

Principal quantum number (n) - Principal quantum number (n) - size and energy of of an size and energy of of an orbital.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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Quantum numbersQuantum numbers Magnetic quantum number (mMagnetic quantum number (mll) ) 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 (mss) ) Can have 2 values.Can have 2 values. either +1/2 or -1/2either +1/2 or -1/2 Q: What are the possible quantum Q: What are the possible quantum numbers for the last electron of numbers for the last electron of a sulfur atom? Iron?a sulfur atom? Iron?

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Example:Describe the electrons defined by the following

quantum numbers:n l m3 0 0 3s electron 2 1 1 2p electron 4 2 -1 4d electron 3 3 2 not allowed (l must be < n)

3 1 2 not allowed (ml must be between -l and l)

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1. What are the shapes of s, p, and d orbitals respectively?

2. How many 1s orbitals are there in an atom? 4p orbitals? 4d orbitals?

3. What is the maximum number of orbitals with:n = 4 l = 1 n = 2 l = 2 n = 3 l = 2 n = 5 l = 1 ml = -1

4. Which orbitals cannot exist?2p 3p 4d 3f 6s 2d

5. Write a set of quantum numbers for a 4f orbital.

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1. What are the shapes of s, p, and d orbitals respectively?s= spherical p = dumbbell d = cloverleaf2. How many 1s orbitals are there in an atom? 4p orbitals? 4d orbitals?1s: 1 4p: 3 4d: 53. What is the maximum number of orbitals with:n = 4 l = 1 3 (the 4p orbitals)n = 2 l = 2 none (l must be < n)n = 3 l = 2 5 (the 3d orbitals)n = 5 l = 1 ml = -1 1 (3 q.n. define a unique orbital)4. Which orbitals cannot exist?2p 3p 4d 3f 6s 2d3f and 2d5. Write a set of quantum numbers for a 4f orbital.n = 4 l = 3 ml = 3, 2, 1, 0, -1, -2, -3

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S orbitals• (BDVD) orbitals

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P orbitals

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D orbitals

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F orbitals

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Pauli Exclusion PrinciplePauli Exclusion Principle In a given atom, no two In a given atom, no two electrons can have the same electrons can have the same set of four quantum numbers set of four quantum numbers ((nn, , ll, , mmll, , mmss).).

ThereforeTherefore, an orbital can , an orbital can hold only two electrons, and hold only two electrons, and they must have opposite they must have opposite spins.spins.

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7.9 Polyelectronic 7.9 Polyelectronic AtomsAtoms 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 The potential energy of the attraction between the nucleus attraction between the nucleus and the electrons.and the electrons.

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

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Polyelectronic atomsPolyelectronic atoms Electron shielding occurs. This Electron shielding occurs. This affects the properties of these affects the properties of these atoms.atoms.

Electrons are attracted to the Electrons are attracted to the nucleus.nucleus.

Electrons are repulsed by other Electrons are repulsed by other electrons.electrons.

Electrons would be bound more Electrons would be bound more tightly if other electrons were tightly if other electrons were not present.not present.

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7.10 The Periodic 7.10 The Periodic Table Table Developed independently by Developed independently by

German Julius Lothar Meyer German Julius Lothar Meyer and Russian Dmitri Mendeleev and Russian Dmitri Mendeleev (1870”s).(1870”s).

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

Predicted properties of Predicted properties of missing elements.missing elements.

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7.11 Aufbau Principle7.11 Aufbau Principle Aufbau is German for building Aufbau is German for building up.up.

As the protons are added one As the protons are added one by one, the electrons fill up by one, the electrons fill up hydrogen-like orbitals.hydrogen-like orbitals.

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

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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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DetailsDetails Valence electrons - the electrons Valence electrons - the electrons in the outermost energy levels in the outermost energy levels (not d).(not d).

Core electrons - the inner Core electrons - the inner electrons.electrons.

Hund’s Rule - The lowest energy Hund’s Rule - The lowest energy configuration for an atom is the configuration for an atom is the one have the maximum number of of one have the maximum number of of unpaired electrons in the orbital.unpaired electrons in the orbital.

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

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DetailsDetails Elements in the same column have Elements in the same column have the same electron configuration.the same electron configuration.

Put in columns because of Put in columns because of similar properties.similar properties.

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

Noble gases have filled energy Noble gases have filled energy levels.levels.

Transition metals are filling Transition metals are filling the d orbitalsthe d orbitals

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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 3d55

Mn = [Ar] 4sMn = [Ar] 4s22 3d 3d55

Cu = [Ar] 4sCu = [Ar] 4s11 3d 3d1010

Half filled orbitals.Half filled orbitals. Scientists aren’t sure of why Scientists aren’t sure of why it happensit happens

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7.12 Periodic Trends in 7.12 Periodic Trends in PropertiesProperties Ionization Energy - The energy Ionization 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 electron from sodium is 1.39 x 101055 kJ/mol . kJ/mol .

The ionization energy for a 3s The ionization energy for a 3s electron from sodium is 4.95 x electron from sodium is 4.95 x 101022 kJ/mol . kJ/mol .

Demonstrates Demonstrates shielding.shielding.

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ShieldingShielding Electrons on the higher energy Electrons on the higher energy levels tend to be farther out.levels tend to be farther out.

Have to “look” through the Have to “look” through the other electrons to “see” the other electrons to “see” the nucleus.nucleus.

They are less effected by the They are less effected by the nucleus.nucleus.

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How orbitals differHow orbitals differ The more positive the nucleus, The more positive the nucleus, the smaller the orbital.the smaller the orbital.

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

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

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Periodic TrendsPeriodic Trends Highest energy electron Highest energy electron removed first. removed first.

First ionization energy (IFirst ionization energy (I11) )

is that required to remove the is that required to remove the first electron.first electron.

Second ionization energy (ISecond ionization energy (I22) )

- the second electron- the second electron

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Trends in ionization Trends in ionization energyenergy 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 The effective nuclear charge increases as you remove electrons.increases as you remove electrons.

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

is a greater nuclear charge is a greater nuclear charge with the same shielding.with the same shielding.

As you go down a group IAs you go down a group I11

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

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It is not that simpleIt is not that simple ZZeffeff changes as you go across changes as you go across

a period, so will Ia period, so will I11

Half filled and filled Half filled and filled orbitals are harder to remove orbitals are harder to remove electrons from.electrons from.

Here’s what it looks like.Here’s what it looks like.

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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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The information it The information it hideshides Know the special groupsKnow the special groups

It is the number and type of It is the number and type of valence electrons that determine valence electrons that determine an atoms chemistry.an atoms chemistry.

You can get the electron You can get the electron configuration from it.configuration from it.

Metals lose electrons have the Metals lose electrons have the lowest IElowest IE

Non metals- gain electrons most Non metals- gain electrons most negative electron affinities.negative electron affinities.

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Electron Affinity & Electron Affinity & Atomic RadiiAtomic Radii Electron affinity - The energy change Electron affinity - The energy change

associated with the addition of an associated with the addition of an electron to a gaseous atom.electron to a gaseous atom.

X(g) + eX(g) + e-- X X--(g)(g) Affinity tends to increase across a Affinity tends to increase across a period and decrease as you go down a period and decrease as you go down a group.group.

Atomic Radii:Atomic Radii: Decrease going from left to right Decrease going from left to right across a period and increase going across a period and increase going down a group.down a group.

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7.13 The Alkali 7.13 The Alkali MetalsMetals Doesn’t include hydrogen - it Doesn’t include hydrogen - it

behaves as a non-metal.behaves as a non-metal. Decrease in IE.Decrease in IE. Increase in radius.Increase in radius. Decrease in density.Decrease in density. Decrease in melting point.Decrease in melting point. Behave as reducing agents.Behave as reducing agents.

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Reducing abilityReducing ability Lower IE = better reducing agents.Lower IE = better reducing agents. Cs>Rb>K>Na>LiCs>Rb>K>Na>Li Works for solids, but not in Works for solids, but not in aqueous solutions.aqueous solutions.

In solution Li>K>NaIn solution Li>K>Na Why?Why? It’s the water - there is an It’s the water - there is an energy change associated with energy change associated with dissolving.dissolving.

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Hydration EnergyHydration Energy It is exothermic.It 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 Li is so big because of it has a high charge density, a lot of high charge density, a lot of charge on a small atom.charge on a small atom.

Li loses its electron more Li loses its electron more easily because of this in easily because of this in aqueous solutions.aqueous solutions.

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The reaction with The reaction with waterwater Na and K react explosively with Na and K react explosively with

water.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 H than that of Na and K.K.

Na and K melt.Na and K melt. H does not tell you speed of H does not tell you speed of reaction.reaction.

More in Chapter 12.More in Chapter 12.