Chapter 5 Electrons in Atoms. Greek Idea Democritus and Leucippus Matter is made up of indivisible particles Dalton - one type of atom for each element.

Chapter 5Chapter 5

Electrons in AtomsElectrons in Atoms

Greek IdeaGreek Idea

Democritus and Democritus and LeucippusLeucippus

Matter is made up of Matter is made up of indivisible particlesindivisible particles

Dalton - one type of Dalton - one type of atom for each atom for each elementelement

Thomson’s ModelThomson’s Model

Discovered electronsDiscovered electrons

Atoms were made of Atoms were made of positive stuffpositive stuff

Negative electron Negative electron floating aroundfloating around

““Plum-Pudding” modelPlum-Pudding” model

Rutherford’s ModelRutherford’s ModelDiscovered dense Discovered dense positive piece at the positive piece at the center of the atomcenter of the atomNucleusNucleusElectrons moved Electrons moved aroundaroundMostly empty spaceMostly empty space

Bohr’s ModelBohr’s Model

Why don’t the electrons fall into the Why don’t the electrons fall into the nucleus?nucleus?

Move like planets around the sun.Move like planets around the sun.

In circular orbits at different levels.In circular orbits at different levels.

Amounts of energy separate one level Amounts of energy separate one level from another.from another.

Bohr’s ModelBohr’s Model

Nucleus

Electron

Orbit

Energy Levels

Bohr’s ModelBohr’s ModelIn

crea

sing

ene

rgy

Nucleus

First

Second

Third

Fourth

Fifth

}Further away Further away from the nucleus from the nucleus means more means more energy.energy.

There is no “in There is no “in between” energybetween” energy

Energy LevelsEnergy Levels

LightLight

The study of light led to the development The study of light led to the development of the quantum mechanical model.of the quantum mechanical model.Light is a kind of electromagnetic radiation.Light is a kind of electromagnetic radiation.Electromagnetic radiation includes many Electromagnetic radiation includes many kinds of waves kinds of waves

All move at 3.00 x 10All move at 3.00 x 1088 m/s ( c) m/s ( c)

Parts of a WaveParts of a Wave

Wavelength

AmplitudeOrigin

Crest

Trough

Parts of WaveParts of WaveOrigin - the base line of the energy.Origin - the base line of the energy.Crest - highest point on a waveCrest - highest point on a waveTrough - Low point on a waveTrough - Low point on a waveAmplitude - distance from origin to crestAmplitude - distance from origin to crestWavelength - distance from crest to crestWavelength - distance from crest to crestWavelength - is abbreviated Wavelength - is abbreviated Greek letter Greek letter lambda.lambda.

FrequencyFrequency

The number of waves that pass a given The number of waves that pass a given point per second.point per second.

Units are cycles/sec or hertz (hz)Units are cycles/sec or hertz (hz)

Abbreviated Abbreviated the Greek letter nuthe Greek letter nu

c = c =

Wavelength and FrequencyWavelength and Frequency

Frequency and WavelengthFrequency and Wavelength

Are inversely relatedAre inversely related

As one goes up the other goes down.As one goes up the other goes down.

Different frequencies of light is different Different frequencies of light is different colors of light.colors of light.

There is a wide variety of frequenciesThere is a wide variety of frequencies

The whole range is called a spectrumThe whole range is called a spectrum

Movie Flame TestMovie Flame Test

Radiowaves

Microwaves

Infrared .

Ultra-violet

X-Rays

GammaRays

Low energy

High energy

Low Frequency

High Frequency

Long Wavelength

Short WavelengthVisible Light

Aurora BorealisAurora Borealis

Energy entering the Energy entering the earth’s atmosphere earth’s atmosphere causes gas atom causes gas atom electrons to become electrons to become excited. When they excited. When they fall to the ground fall to the ground state they give of state they give of photons of light.photons of light.MovieMovie Aurora Aurora

Atomic SpectrumAtomic Spectrum

How color tells us How color tells us about atomsabout atoms

PrismPrism

White light is made White light is made up of all the colors up of all the colors of the visible of the visible spectrum.spectrum.

Passing it through a Passing it through a prism separates it.prism separates it.

If the light is not whiteIf the light is not white

By heating a gas By heating a gas with electricity we with electricity we can get it to give off can get it to give off colors.colors.

Passing this light Passing this light through a prism through a prism does something does something different.different.

Atomic SpectrumAtomic Spectrum

Each element gives Each element gives off its own off its own characteristic colors.characteristic colors.Can be used to Can be used to identify the atom.identify the atom.How we know what How we know what stars are made of.stars are made of.Movie Emission SpeMovie Emission Spectrumctrum

Atomic Emission SpectrumAtomic Emission Spectrum

• These are called discontinuous spectra

• Or line spectra

• unique to each element.

• These are emission spectra

• The light is emitted given off.

Light is a ParticleLight is a Particle

Energy is quantized.Energy is quantized.

Light is energyLight is energy

Light must be quantizedLight must be quantized

These smallest pieces of light are called These smallest pieces of light are called photons.photons.

Energy and frequency are directly related. Energy and frequency are directly related.

Energy and FrequencyEnergy and Frequency

E = hE = hE is the energy of the photonE is the energy of the photon

is the frequencyis the frequency

h is Planck’s constant h is Planck’s constant

h = 6.6262 x 10 h = 6.6262 x 10 -34 -34 Joules sec.Joules sec.

joule is the metric unit of Energyjoule is the metric unit of Energy

The Math in Chapter 5The Math in Chapter 5

Only 2 equationsOnly 2 equations

c = c =

E = h E = h

Plug and chug.Plug and chug.

ExamplesExamples

What is the wavelength of blue light with What is the wavelength of blue light with a frequency of 8.3 x 10a frequency of 8.3 x 101515 hz? hz?

What is the frequency of red light with a What is the frequency of red light with a wavelength of 4.2 x 10wavelength of 4.2 x 10-5 -5 m?m?

What is the energy of a photon of each What is the energy of a photon of each of the above? of the above?

Given h = 6.6262 x 10 Given h = 6.6262 x 10 -34 -34 Joules sec and the Joules sec and the Speed of light equals 3.00 x 10Speed of light equals 3.00 x 1088 m/s ( c) m/s ( c)

An An Explanation Explanation

of Atomic of Atomic SpectraSpectra

Where the Electron StartsWhere the Electron Starts

When we write electron configurations we When we write electron configurations we are writing the lowest energy.are writing the lowest energy.

The energy level where an electron starts The energy level where an electron starts from is called its ground state.from is called its ground state.

Movie Energy LevelsMovie Energy Levels

Changing the EnergyChanging the Energy

Let’s look at a hydrogen atomLet’s look at a hydrogen atom

Changing the Energy

Heat or electricity or light can move the Heat or electricity or light can move the electron up energy levelselectron up energy levels

Changing the Energy

As the electron falls back to ground state it As the electron falls back to ground state it gives the energy back as lightgives the energy back as light

May fall down in stepsMay fall down in steps

Each with a different energyEach with a different energy

Changing the Energy

{{{

Further they fall, more energy, higher Further they fall, more energy, higher frequency.frequency.

This is simplifiedThis is simplified

The orbitals also have different energies The orbitals also have different energies inside energy levels.inside energy levels.

All the electrons can move around.All the electrons can move around.

Ultraviolet Visible Infrared

What Makes These Glow?What Makes These Glow?

What is lightWhat is light

Light is a particle - it comes in chunks.Light is a particle - it comes in chunks.

Light is a wave- we can measure its wave Light is a wave- we can measure its wave length and it behaves as a wavelength and it behaves as a wave

If we combine E=mcIf we combine E=mc22 , c= , c= , E = 1/2 mv, E = 1/2 mv2 2

and E = hand E = h

We can get De Broglie’s equation We can get De Broglie’s equation = = h/mvh/mv

The wavelength of a particle. The wavelength of a particle.

Matter is a WaveMatter is a Wave

Does not apply to large objectsDoes not apply to large objects

Things bigger than an atomThings bigger than an atom

A baseball has a wavelength of about A baseball has a wavelength of about

1x101x10--32 32 m when moving 30 m/sm when moving 30 m/s

An electron at the same speed has a An electron at the same speed has a

wavelength of 1x10wavelength of 1x10--3 3 cmcm

Big enough to measure. Big enough to measure.

The Physics of the Very SmallThe Physics of the Very Small

Quantum mechanics explains how the Quantum mechanics explains how the very small behaves.very small behaves.

Classic physics is what you get when you Classic physics is what you get when you add up the effects of millions of packages.add up the effects of millions of packages.

Quantum mechanics is based on Quantum mechanics is based on probability becauseprobability because

Heisenberg Uncertainty Heisenberg Uncertainty PrinciplePrinciple

It is impossible to know exactly the It is impossible to know exactly the location and velocity of a particle.location and velocity of a particle.

The better we know one, the less we know The better we know one, the less we know the other.the other.

The act of measuring changes the The act of measuring changes the properties.properties.

Measuring an ElectronMeasuring an Electron

To measure where an electron is, we use lightTo measure where an electron is, we use lightBut the light moves the electronBut the light moves the electronAnd hitting the electron changes the frequency of the lightAnd hitting the electron changes the frequency of the light

Moving Electron

Photon

Before

ElectronChanges Velocity

Photon Changes Wavelength

After

The Quantum Mechanical The Quantum Mechanical ModelModel

Remember energy is quantized and comes in Remember energy is quantized and comes in chunks.chunks.A quanta is the amount of energy needed to A quanta is the amount of energy needed to move from one energy level to another.move from one energy level to another.Since the energy of an atom is never “in Since the energy of an atom is never “in between” there must be a quantum leap in between” there must be a quantum leap in energy.energy.Schrodinger derived an equation that Schrodinger derived an equation that described the energy and position of the described the energy and position of the electrons in an atom.electrons in an atom.

Atoms Are Never “In Between” Atoms Are Never “In Between” LevelsLevels

Things that are very small Things that are very small behave differently from things behave differently from things big enough to see.big enough to see.The quantum mechanical The quantum mechanical model is a mathematical model is a mathematical solutionsolutionIt is not like anything you can It is not like anything you can see.see.


Has energy levels forHas energy levels for electrons. electrons.Orbits are not circular.Orbits are not circular.It can only tell us theIt can only tell us the probability of finding probability of finding

an electron a certain distance from the an electron a certain distance from the nucleus.nucleus.


The atom is found inside The atom is found inside a blurry “electron cloud”a blurry “electron cloud”

An area where there is a An area where there is a chance of finding an chance of finding an electron.electron.

Can be divided into Can be divided into smaller regions in the smaller regions in the electron cloud.electron cloud.


Atomic OrbitalsAtomic Orbitals

Principle Quantum Number (n) = the energy Principle Quantum Number (n) = the energy level of the electronlevel of the electronWithin each energy level the complex math of Within each energy level the complex math of Schrodinger’s equation describes several Schrodinger’s equation describes several geometric shapes.geometric shapes.The group shape is called the sublevel s,p,d,fThe group shape is called the sublevel s,p,d,fIndividual shapes are the electron orbitalsIndividual shapes are the electron orbitalsThe orbitals represent regions where there is a The orbitals represent regions where there is a high probability of finding an electron.high probability of finding an electron.

Sublevels and Energy LevelsSublevels and Energy Levels

1 s orbital is 1 s orbital is found on every energy levelfound on every energy level

Spherical shapedSpherical shapedEach s orbital can hold 2 electronsEach s orbital can hold 2 electronsCalled the 1s, 2s, 3s, etc.. orbitals. The 1,2 Called the 1s, 2s, 3s, etc.. orbitals. The 1,2 and 3 designate the energy levels.and 3 designate the energy levels.

s Sublevels Sublevel

6s Sublevel6s Sublevel

http://www.shef.ac.uk/chemistry/orbitron/http://www.shef.ac.uk/chemistry/orbitron/

Alkali metals all end in sAlkali metals all end in s11

Alkaline earth metals all end in sAlkaline earth metals all end in s22

really should include He, but it fits really should include He, but it fits better later.better later.

He has the properties of the noble He has the properties of the noble gases.gases.

s2s1 S- blockS- block

s, p, d, & f blockss, p, d, & f blocks

p Sublevelp SublevelStart at the second energy level Start at the second energy level

3 different directions3 different directions

3 different shapes3 different shapes

Each can hold 2 electronsEach can hold 2 electrons

6p Sublevel6p Sublevel


s & p orbitals for neons & p orbitals for neon

Glencoe ‘Chemistry Matter and Change’ 2002, page 137

The P-blockThe P-block p1 p2 p3 p4 p5 p6

Each row (or period) is the energy level Each row (or period) is the energy level for s and p orbitals.for s and p orbitals.

1

2

3

4

5

6

7

d Subleveld SublevelStart at the third energy level Start at the third energy level

5 different shapes5 different shapes

Each can hold 2 electronsEach can hold 2 electrons

6d Sublevel6d Sublevel


Transition Metals -d blockTransition Metals -d block

d1 d2 d3s1

d5 d5 d6 d7 d8s1

d10 d10

d orbitals fill up after previous energy level, d orbitals fill up after previous energy level, so first d is 3d even though it’s in row 4.so first d is 3d even though it’s in row 4.

1

2

3

4

5

6

7

3d

f Sublevelf Sublevel

Start at the fourth energy levelStart at the fourth energy level

Have seven different shapesHave seven different shapes

2 electrons per shape2 electrons per shape

f Sublevelf Sublevel

6f Sublevel6f Sublevel

F - blockF - block

inner transition elementsinner transition elements

f1 f5f2 f3 f4

f6 f7 f8 f9 f10 f11 f12 f14

f13

f orbitals start filling at 4ff orbitals start filling at 4f

1

2

3

4

5

6

7 4f

5f

s, p, d, & f blockss, p, d, & f blocks

6g Sublevel6g Sublevel

Sublevel g starts Sublevel g starts on the 5on the 5thth level. level.9 shapes9 shapes18 electrons max18 electrons maxhttp://http://www.shef.ac.uk/www.shef.ac.uk/chemistry/chemistry/orbitron/orbitron/

SummarySummary

s

p

d

f

# of shapes

Max electrons

Starts at energy level

1 2 1

3 6 2

5 10 3

7 14 4

SL

By Energy LevelBy Energy Level

First Energy LevelFirst Energy Level

only s orbitalonly s orbital

only 2 electronsonly 2 electrons

1s1s22

Second Energy Second Energy LevelLevel

s and p orbitals are s and p orbitals are availableavailable

2 in s, 6 in p2 in s, 6 in p

2s2s222p2p66

8 total electrons8 total electrons


Third energy levelThird energy level

s, p, and d orbitalss, p, and d orbitals

2 in s, 6 in p, and 10 2 in s, 6 in p, and 10 in din d

3s3s223p3p663d3d1010


Fourth energy levelFourth energy level

s,p,d, and f orbitalss,p,d, and f orbitals

2 in s, 6 in p, 10 in 2 in s, 6 in p, 10 in d, and 14 in fd, and 14 in f

4s4s224p4p664d4d10104f4f1414



Any more than the Any more than the fourth and not all the fourth and not all the orbitals will fill up.orbitals will fill up.

You simply run out You simply run out of electronsof electrons

The orbitals do not The orbitals do not fill up in a neat fill up in a neat order.order.

The energy levels The energy levels overlapoverlap

Lowest energy fill Lowest energy fill first.first.

Writing Electron Writing Electron Configurations the Easy Configurations the Easy

WayWay

Yes there is a shorthandYes there is a shorthand

Electron Configurations repeatElectron Configurations repeat

The shape of the periodic table is a The shape of the periodic table is a representation of this repetition.representation of this repetition.

When we get to the end of the column When we get to the end of the column the outermost energy level is full.the outermost energy level is full.

This is the basis for our shorthand.This is the basis for our shorthand.

The Shorthand MethodThe Shorthand Method

Write symbol of the noble gas Write symbol of the noble gas before the element, in [ ].before the element, in [ ].

Then, the rest of the electrons.Then, the rest of the electrons.

Aluminum’s full configuration:Aluminum’s full configuration: 1s1s222s2s222p2p663s3s223p3p11

previous noble gas Ne is: 1sprevious noble gas Ne is: 1s222s2s222p2p66

so, Al is: [Ne] 3sso, Al is: [Ne] 3s223p3p11

The Shorthand AgainThe Shorthand Again

Sn- 50 electrons

The noble gas before it is Kr

[ Kr ]

Takes care of 36

Next 5s2

5s2

Then 4d10

4d10Finally 5p2

5p2

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

Aufbau Diagram shows the energy of each sublevel and the order they fill with electrons

Each box represents an atomic orbital

Electron ConfigurationsElectron Configurations

The way electrons are arranged in The way electrons are arranged in atoms.atoms.Aufbau principleAufbau principle- electrons enter the - electrons enter the lowest energy first.lowest energy first.This causes difficulties because of the This causes difficulties because of the overlap of orbitals of different energies.overlap of orbitals of different energies.Pauli Exclusion PrinciplePauli Exclusion Principle- at most 2 - at most 2 electrons per orbital - different spinselectrons per orbital - different spins

Electron ConfigurationElectron Configuration

Hund’s RuleHund’s Rule- When electrons occupy - When electrons occupy orbitals of equal energy they don’t orbitals of equal energy they don’t pair up until they have topair up until they have to

Let’s determine the electron Let’s determine the electron configuration for Phosphorus configuration for Phosphorus

Need to account for 15 electronsNeed to account for 15 electrons

The first two electrons go The first two electrons go into the 1s orbitalinto the 1s orbitalNotice the opposite spinsNotice the opposite spinsSame as HeliumSame as Helium1s1s22

only 13 moreonly 13 more

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

The next electrons The next electrons go into the 2s orbitalgo into the 2s orbital

‘ ‘Be’ on periodic tableBe’ on periodic table

1s1s222s2s22

only 11 moreonly 11 more

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

The next electrons go into the 2p orbitals

Neon on periodic table 1s22s22p6

only 5 more

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

The next electrons go into the 3s orbital

‘Mg’ on periodic table Only 3 more 1s22s22p63s2

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

The last three electrons go into the 3p orbitals.

They each go into separate orbitals

3 unpaired electrons

1s22s22p63s23p3

The easy way to remember The easy way to remember

1s2s 2p3s 3p 3d4s 4p 4d 4f

5s 5p 5d 5f 6s 6p 6d 6f7s 7p 7d 7f

• 1s2

• 2 electrons

Fill from the bottom up Fill from the bottom up following the arrowsfollowing the arrows

1s2s 2p3s 3p 3d4s 4p 4d 4f

5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

• 1s2 2s2

• 4 electrons


1s2s 2p3s 3p 3d4s 4p 4d 4f

5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

• 1s2 2s2 2p6 3s2

• 12 electrons


1s2s 2p3s 3p 3d4s 4p 4d 4f

5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

• 1s2 2s2 2p6 3s2

3p6 4s2

• 20 electrons


1s2s 2p3s 3p 3d4s 4p 4d 4f

5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

• 1s2 2s2 2p6 3s2

3p6 4s2 3d10 4p6

5s2

• 38 electrons


1s2s 2p3s 3p 3d4s 4p 4d 4f

5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

• 1s2 2s2 2p6 3s2

3p6 4s2 3d10 4p6

5s2 4d10 5p6 6s2

• 56 electrons


1s2s 2p3s 3p 3d4s 4p 4d 4f

5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

• 1s2 2s2 2p6 3s2

3p6 4s2 3d10 4p6

5s2 4d10 5p6 6s2

4f14 5d10 6p6 7s2

• 88 electrons


1s2s 2p3s 3p 3d4s 4p 4d 4f

5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

• 1s2 2s2 2p6 3s2

3p6 4s2 3d10 4p6

5s2 4d10 5p6 6s2

4f14 5d10 6p6 7s2

5f14 6d10 7p6 • 118 electrons

Exceptions to the Exceptions to the Rule in Electron Rule in Electron

ConfigurationConfiguration

Orbitals Fill Order Orbitals Fill Order

Lowest energy to higher energyLowest energy to higher energy

Adding electrons can change the energy Adding electrons can change the energy of the orbitalof the orbital

Half filled orbitals have a lower energyHalf filled orbitals have a lower energy

Makes them more stableMakes them more stable

Sometimes changes the filling orderSometimes changes the filling order

Write These Electron Write These Electron ConfigurationsConfigurations

Titanium - 22 electronsTitanium - 22 electrons1s1s222s2s222p2p663s3s223p3p664s4s223d3d22

Vanadium - 23 electrons Vanadium - 23 electrons 1s1s222s2s222p2p663s3s223p3p664s4s223d3d33

Chromium - 24 electronsChromium - 24 electrons1s1s222s2s222p2p663s3s223p3p664s4s223d3d4 4 is expectedis expectedBut this is wrong!!But this is wrong!!

Chromium is ActuallyChromium is Actually

1s1s222s2s222p2p663s3s223p3p664s4s113d3d55

Why?Why?

This gives us two half filled orbitalsThis gives us two half filled orbitals

Slightly lower in energySlightly lower in energy

Holds true for other group 6 elements Cr, Holds true for other group 6 elements Cr, Mo, W, and probably SgMo, W, and probably Sg

The same principal applies to copper Cu The same principal applies to copper Cu and group 11 elementsand group 11 elements

Transition Metals -d blockTransition Metals -d block

d1 d2 d3s1

d5 d5 d6 d7 d8s1

d10 d10

Cu’s Electron ConfigurationCu’s Electron Configuration

Copper has 29 electrons so we expectCopper has 29 electrons so we expect

1s1s222s2s222p2p663s3s223p3p664s4s223d3d99

But the actual configuration isBut the actual configuration is

1s1s222s2s222p2p663s3s223p3p664s4s113d3d1010

This gives one filled orbital and one half This gives one filled orbital and one half filled orbital.filled orbital.Same is true for ‘Silver’ Ag and ‘Gold’ Au Same is true for ‘Silver’ Ag and ‘Gold’ Au and probably ‘Unununium’ Uuuand probably ‘Unununium’ Uuu

Lewis/Electron Dot DiagramLewis/Electron Dot Diagram

Chapter 5 Electrons in Atoms. Greek Idea Democritus and Leucippus Matter is made up of indivisible particles Dalton - one type of atom for each element.

Documents

energy light

frequency slide

light light

energy energy levels

element slide

space slide

different energy

energy nucleus