HSTMr.Watson Chapter 8 Electron Configuration and Periodicity

HSTMr.Watson

Chapter 8Chapter 8

Electron Configuration and Periodicity

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OrbitalsOrbitals

region of probability of finding an electron around the nucleus

4 types => s p d fmaximum of 2 electrons per orbital

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Pure Atomic OrbitalsPure Atomic Orbitals

shape # of orbitals / energy level

s spherical 1

p dumbbell 3

d complex 5

f very complex 7

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Pauli Exclusion PrinciplePauli Exclusion Principle

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Electronic ConfigurationsElectronic Configurations

The shorthand representation of the occupancy of the energy levels (shells and subshells) of an atom by electrons.

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Electronic ConfigurationElectronic Configuration

shells => energy levels

subshells => orbitals

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Regions by Electron TypeRegions by Electron Type

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Electron Filling Order Electron Filling Order DiagramDiagram

1s

2s 2p

3s 3p 3d

4s 4p 4d 4f

5s 5p 5d 5f

6s 6p 6d

7s

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Electronic ConfigurationElectronic Configuration

H atom

1 electron

1s1

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Electronic ConfigurationElectronic Configuration

He atom

2 electrons

1s2

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Electronic ConfigurationElectronic Configuration

Li atom

3 electrons

1s2, 2s1

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Electronic ConfigurationElectronic Configuration

Cl atom

17 electrons

1s2, 2s2, 2p6, 3s2, 3p5

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Electronic ConfigurationElectronic Configuration

As atom

33 electons

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p3

or

[Ar] 4s2, 3d10, 4p3

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Mn: [Ar]4s2 3d?

How many d electrons does Mn have?

4, 5, 6

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Electronic ConfigurationElectronic Configuration

negative ions

add electron(s), 1 electron for each negative charge

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Electronic ConfigurationElectronic Configuration

S-2 ion

(16 + 2)electrons

1s2, 2s2, 2p6, 3s2, 3p6

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Electronic ConfigurationElectronic Configuration

positive ions

remove electron(s), 1 electron for each positive charge

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Electronic ConfigurationElectronic Configuration

Mg+2 ion

(12-2)electrons

1s2, 2s2, 2p6

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How many valence electrons are in Cl, [Ne]3s2 3p5?

2, 5, 7

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For Cl to achieve a noble gas configuration, it is more likely that

electrons would be added

electrons would be removed

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Trends in theTrends in thePeriodic TablePeriodic Table

atomic radiusionic radiusionization energyelectron affinity

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Atomic RadiusAtomic Radiusdecrease left to right across a period

– as nuclear charge increases, number of electrons increase; however, the nucleus acts as a unit charge while the electrons act independently, pulling electrons towards the nucleus, decreasing size

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Atomic RadiusAtomic Radiusincrease top to bottom down a group

– each additional electron “shell” shields the outer electrons from the nuclear charge

Zeff = Z - Swhere Zeff => effective nuclear charge

Z => nuclear charge, atomic numberS => shielding constant

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Atomic RadiusAtomic Radiusincreases from upper right corner to the

lower left corner

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Atomic Radius vs. Atomic Number

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Atomic RadiusAtomic Radius

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Ionic RadiusIonic Radiussame trends as for atomic radiuspositive ions smaller than atomnegative ions larger than atom

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Ionic RadiusIonic Radius

Isoelectronic Seriesseries of negative ions, noble gas atom, and

positive ions with the same electronic confiuration

size decreases as “positive charge” of the nucleus increases

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Ge is a semiconductor. If half of the Ge atoms of a sample of Ge are replaced with Ga atoms, with what element should the other half of the Ga atoms be replaced in order for this new compound to be isoelectronic with Ge?

Sn, As, Se

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Ionization EnergyIonization Energyenergy necessary to remove an electron to

form a positive ionlow value for metals, electrons easily

removedhigh value for non-metals, electrons

difficult to removeincreases from lower left corner of periodic

table to the upper right corner

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Ionization EnergiesIonization Energies

first ionization energyenergy to remove first electron from an

atom

second ionization energyenergy to remove second electron from a +1

ion

etc.

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Ionization Energy vs. Atomic NumberIonization Energy vs. Atomic Number

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Electron AffinityElectron Affinity

energy released when an electron is added to an atom

same trends as ionization energy, increases from lower left corner to the upper right corner

metals have low “EA”nonmetals have high “EA”

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MagnetismMagnetism

Result of the spin of electronsdiamagnetism - no unpaired electronsparamagnetism - one or more unpaired

electronsferromagentism - case of paramagnetism

where the substance retains its magnetism

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MagnetismMagnetism                                                                                                   

Paramagnetism

Ferromagnetism

Without applied field Without applied field

With applied fieldWith applied field