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Sublevels and OrbitalsSublevels and OrbitalsEffective Nuclear ChargeEffective Nuclear Charge

Inner (core) electrons act to shield outer(valence) electrons from the positive chargeof the nucleus.

Some orbitals penetrate to the nucleus morethan others, therefore s < p < d < f.s < p < d < f.

As a result, there are different energy levelsfor the different sublevels for any givenprincipal quantum number.

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SublevelsSublevelsen

ergy

1s

2s

1s

2s

1s

2s2p 2p

H Li F

2p

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Aufbau PrincipleAufbau Principle

The Aufbau Principal is used to write theelectron configurations of atoms.

For any element, the number of electrons inthe neutral atom equals the atomic

number.

Start filling orbitals, from lowest to highest.

If two or more orbitals exist at the sameenergy level, they are degenerate. Do notpair the electrons until you have to.

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Orbital Filling OrderOrbital Filling Order. s p d f

1 1s2 2s 2p3 3s 3p 3d4 4s 4p 4d 4f5 5s 5p 5d 5f6 6s 6p 6d 6f7 7s 7p 7d 7f

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Hund’s RuleHund’s Rule

When putting electrons into orbitals with thesame energy, place one electron in each orbital before putting two in any one.

In the orbital diagram, each electron musthave opposite spins.

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Applying The Aufbau PrincipalApplying The Aufbau Principal

1s

2s2p

1s

2s2p

1s

2s2p

ener

gy

C O F

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Sublevels on the Periodic Table Sublevels on the Periodic Table

H

Li

Na

Cs

Rb

K

TlHgAuLaBa

Fr

PtIrOsReWTa

He

RnAtPoBiPb

Be

Mg

Sr

Ca

CdAgY PdRhRuTcMoNb

Ra

ZnCu

Hf

Zr

TiSc NiCoFeMnCrV

In XeITeSbSn

Ga KrBrSeAsGe

Al ArClSPSi

B NeFONC

GdCm

TbBk

SmPu

EuAm

NdU

PmNp

CeTh

PrPa

YbNo

AcErFm

TmMd

DyCf

HoEs

f

d

p

LuLr

s

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Using the Periodic Table to apply Using the Periodic Table to apply the Aufbau Principlethe Aufbau Principle

Main Group ElementsAdd electrons to the nsns orbital as you move through s-block.Add electrons to the npnp orbital as you

move through the p-block.

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Using the Periodic Table to apply Using the Periodic Table to apply the Aufbau Principlethe Aufbau Principle

Transition ElementsAdd electrons to the (n-1)d(n-1)d orbital as

you move through d-block.Add electrons to the (n-2)f(n-2)f orbital as

you move through f-block.

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Writing Electron ConfigurationsWriting Electron Configurations

Expanded FormatExpanded Format

O 1s22s22p4 Ti 1s22s22p63s23p64s23d2

Br 1s22s22p63s23p64s23d104p5

Abbreviated FormatAbbreviated Format

O [He]2s22p4 Ti [Ar]4s23d2 Br [Ar]4s23d104p5

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Electron Configurations for IonsElectron Configurations for Ions

Electron configurations can also be writtenfor ions.Start with the ground-state configuration

for the atom.For cations, remove the number of the

outermost electrons equal to the charge.For anions, add the number of outermost

electrons equal to the charge.

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Electron Configurations for AnionsElectron Configurations for Anions

Example: ClExample: Cl- - (chloride)(chloride)

First, write the electron configuration forchlorine:

Cl [Ne]3s23p5

Because the charge is 1-, add one electron.

Cl- [Ne]3s23p6

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Electron Configurations for CationsElectron Configurations for Cations

Example: BaExample: Ba2+2+ (barium) (barium)

First, write the electron configuration forbarium.

Ba [Xe]6s2

Because the charge is 2+, remove twoelectrons.

Ba2+ [Xe]

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Isoelectronic ConfigurationsIsoelectronic ConfigurationsSpecies having the same electronconfigurations.

Each of the following has an electronconfiguration of 1s22s22p6

OO2-2- FF-- NeNe

NaNa++ MgMg2+2+ Al Al3+3+

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Electron Dot DiagramsElectron Dot Diagrams

A simple way to show the valence electronspresent in an atom.

Valence electrons are those electrons foundin the highest numbered principal energylevel (PEL).

Valence electrons are found only in the s and

p sublevels and in most cases are theelectrons responsible for bonding.

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Electron Dot DiagramsElectron Dot Diagrams

The chemical symbol represents the kernel of

the atom.

The kernel of an atom consists of the nucleus

and the core electrons.

Example

X

s px

py

pz

Start with s and proceed cw!

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Electron Dot DiagramsElectron Dot DiagramsExamples

Na [Ne]3s1

Br [Ar]4s23d104p5

Cr [Ar]4s13d5

.

...

. ....

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Heisenberg Uncertainty PrincipleHeisenberg Uncertainty Principle In order to observe an electron, one would need to hit it with photons having a very short wavelength. Short wavelength photons would have a high frequency and a great deal of energy. If one were to hit an electron, it would cause the motion and the speed of the electron to change. Lower energy photons would have a smaller effect but would not give precise data.

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Quantum NumbersQuantum NumbersPrincipal Quantum Number (n)Principal Quantum Number (n)

Tells the size of an orbital and determines its energy. n = 1, 2, 3 …

Angular Momentum (l)Angular Momentum (l) The number of subshells that a principal level contains. It tells the shape of the orbitals. l = 0 to n - 1

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Quantum NumbersQuantum Numbers

Magnetic Quantum Number (mMagnetic Quantum Number (mll))

Describes the orientation of the orbital.

ml = -l to +l (all integers, including zero)

For example, if l = 3, then ml would have values of -3, -2, -1, 0, 1, 2, 3

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Quantum NumbersQuantum Numbers

. n l ml Sublevel Orbitals1 0 0 1s 12 0 0 2s 1

1 -1,0,1 2p 33 0 0 3s 1

1 -1,0,1 3p 32 -2,-1,0,1,2 3d 5

4 0 0 4s 11 -1,0,1 4p 32 -2,-1,0,1,2 4d 53 -3,-2,-

1,0,1,2,34f 7

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The s OrbitalThe s Orbital

The s orbital is a sphere. Every PEL has ones orbital.

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The p OrbitalsThe p Orbitals

There are three p orbitals: px, py and pz

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Electron SpinElectron Spin

Pauli added one additional quantum numberthat would allow only two electrons to be inan orbital.Spin quantum number (mSpin quantum number (mss))..

It can have values of +1/2 and -1/2Pauli Exclusion PrinciplePauli Exclusion Principle

Pauli also proposed that no two electrons in an atom can have the same set of four quantum numbers.

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WavesWavesWavelengthWavelength (l) (l)

The distance measured from crest to crest or from trough to trough (m, cm, nm).

AmplitudeAmplitude

The vertical distance from the node to the height of a wave (m, cm, nm).

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FrequencyFrequency (f) (f)

The number of cycles or complete vibrations that pass a point each

second (s-1, vib/s).

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Electromagnetic RadiationElectromagnetic Radiation

A form of energy consisting of perpendicularelectrical and magnetic fields that change, atthe same time and in phase with time.

The SI unit of frequency (f) is the hertz (Hz) 1 Hz = 1 s1 Hz = 1 s-1 -1 = 1/s= 1/s

Wavelength and frequency are related c = f λc = f λ c = 3.00 x10c = 3.00 x1088 m/s m/s

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Energy ProblemsEnergy ProblemsCalculate the frequency of a quantum of

light, aphoton, with a wavelength of 6.00 x 10-7 m.

λ = 6.00 × 10-7 m c = 3.00 × 108 m/s

C = f × λ f = =

C λ

=5.00 × 1014 /s3.00 × 108 m/s 6.00 × 10-7 m

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Energy ProblemsEnergy ProblemsCalculate the energy of a photon, with awavelength of 6.00 x 10-7 m.

λ = 6.00 × 10-7 m c = 3.00 × 108 m/sh = 6.63 × 10-34 J•s

E = h × f c = f × λ f = c/λ

E = h × c/λ

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E = h × c/λ

E = 6.63 × 10-34 J•s × 3.00 × 108 m/s 6.0 × 10-7 m

E = 3.3 × 10-19 J