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Chapter 7Chapter 7

Atomic StructureAtomic Structure

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LightLight Made up of electromagnetic Made up of electromagnetic

radiation.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 examples.and gamma rays are all examples. Light is only the part our eyes can Light is only the part our eyes can

detect.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 = 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 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 couldnít be explained of hot objects couldnít 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 Planckís constant and h is Planckís 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 quantized in particles called photons.photons.

Each photon has energy = hEach photon has energy = 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 Broglieís equation De Broglieís 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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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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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 line, it creates a rainbow effect line, 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

hole.hole. A wave through both holes.A wave through both holes. 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.

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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 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 in the atom is Energy in the in the atom is

quantized. 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.

Didnít fall in to the nucleus because Didnít 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 didnít know why but only certain He didnít 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 energy.gives 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 closer to the electron you make it closer 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 Doesnít work.Doesnít work. Only works for hydrogen atoms.Only works for hydrogen atoms. Electrons donít move in circles.Electrons donít 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 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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Whatís possible?Whatís 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 electron.the wave function of the electron. Much math but what is important are Much math but what is important are

the solution.the solution.

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Schroedingerís EquationSchroedingerís Equation The wave function is a F(x, y, z)The wave function is a F(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 canít know how the electron is We canít 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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MathematicallyMathematically x ∑ x ∑ (mv) > h/4(mv) > h/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 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 .100 m/sspeed of .100 m/s

What is the uncertainty in the What is the uncertainty in the position of a baseball, mass .145 kg position of a baseball, mass .145 kg with an uncertainty in the speed with an uncertainty in the speed of .100 m/sof .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

Schroedingerís equationSchroedingerís 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 of an orbital.and energy of 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 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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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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Polyelectronic atomsPolyelectronic atoms Canít solve Schroedingerís equation Canít solve Schroedingerís equation

exactly.exactly. 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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+10

11 electrons

+10 10 otherelectrons

e-Zeff

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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 (1870îs).Dmitri Mendeleev (1870îs).

Didnít know much about atom.Didnít 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

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

He with 2 electrons

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More on Electron ConfigurationMore on Electron Configuration

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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. Hundís RuleHundís 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 of have the maximum number of 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

ï 1s2

ï 2ï electrons

2s2

ï 4

2p6 3s2

ï 12

3p6 4s2

ï 20

3d10 4p6

5s2

ï 38

4d10 5p6 6s2

ï 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 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 arenít sure of why it Scientists arenít sure of why it

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

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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

Weíll just pretend that all except Cu Weíll 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 itís pattern on the if we determine itís 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 ZeffSo we can measure Zeff 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 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 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 isnít it?Why isnít it?

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PenetrationPenetration There are levels to the electron There are levels to the electron

distribution for each orbital.distribution 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

78

Rad

ial P

roba

bili

ty

Distance from nucleus

3p

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Rad

ial P

roba

bili

ty

Distance from nucleus

3d

80

Rad

ial P

roba

bili

ty

Distance from nucleus

4s

3d

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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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Zef

f

1

2

4

5

1

84

Zef

f

1

2

4

5

1

If shielding is perfect Z= 1

85

Zef

f

1

2

4

5

1

No

shie

ldin

gZ

= Z ef

f

86

Zef

f

1

2

4

5

16

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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

ï II11 = 735 kJ/mole = 735 kJ/moleï II22 = 1445 kJ/mole = 1445 kJ/moleï 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

ï II11 = 580 kJ/mole = 580 kJ/mole

ï II22 = 1815 kJ/mole = 1815 kJ/mole

ï II33 = 2740 kJ/mole = 2740 kJ/mole

ï 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 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 from.harder to remove electrons from.

hereís what it looks like.hereís what it looks like.

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Firs

t Ion

izat

ion

ener

gy

Atomic number

93

Firs

t Ion

izat

ion

ener

gy

Atomic number

94

Firs

t Ion

izat

ion

ener

gy

Atomic number

95

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 atoms electrons that determine an atoms 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 Non metals- gain electrons most

negative electron affinities.negative electron affinities.

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The Alkali MetalsThe Alkali Metals Doesnít include hydrogen- it behaves Doesnít 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? Itís the water -there is an energy Itís the water -there is an energy

change associated with dissolvingchange associated with dissolving

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Hydration EnergyHydration Energy It is exothermicIt 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 doesnít.Li doesnít. 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.