center of nucleus

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AnnouncementsAnnouncements & Agenda& Agenda (01/24/07)(01/24/07)

You should currently be reading Ch 4!You should currently be reading Ch 4!Quiz over Ch 3 moved to Friday!Quiz over Ch 3 moved to Friday!Pick up Graded Quizzes if you haven’tPick up Graded Quizzes if you haven’tWelcome Visitors!Welcome Visitors!

Today:Today: Recap of Mon: Electron Energy Levels (3.7)Recap of Mon: Electron Energy Levels (3.7) Periodic trends (3.3, 3.8)Periodic trends (3.3, 3.8) Start Ch 4 (Finally!)Start Ch 4 (Finally!)

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Last Time: Medical Uses of RadiationLast Time: Medical Uses of Radiation

Nuclear medicine has two main arenasNuclear medicine has two main arenas

Diagnostic methodsDiagnostic methods

Small amounts of radioisotopes Small amounts of radioisotopes administered to help image an organ or administered to help image an organ or follow a physiological processfollow a physiological process

Therapeutic methodsTherapeutic methods

Larger radiation doses to deliver fatal Larger radiation doses to deliver fatal punch to diseased tissuepunch to diseased tissue

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*EMISSION**EMISSION*

ABSORPTIONABSORPTION

Last Time: Electrons Last Time: Electrons in Atomsin Atoms

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Last Time: Explanation for Discrete Last Time: Explanation for Discrete Energies: the Bohr ModelEnergies: the Bohr Model

First model of the electron structure of atomsFirst model of the electron structure of atoms

Gives energy levels (shells) where an electron is Gives energy levels (shells) where an electron is most likely to be foundmost likely to be found

Incorrect, but a key to understanding the atomIncorrect, but a key to understanding the atom

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Last Time: Modern Understanding Last Time: Modern Understanding of Electron Levels (Shells)of Electron Levels (Shells)

Electrons are organized in shellsElectrons are organized in shells

Electrons in a Electrons in a particularparticular shell are shell are similarsimilar in in

energy and distance from nucleusenergy and distance from nucleus

Low-energy electrons closest to the nucleusLow-energy electrons closest to the nucleus

Identify shells by a “principle quantum Identify shells by a “principle quantum

number”: 1, 2, 3, 4, 5…..number”: 1, 2, 3, 4, 5…..

The first shell (1) is lowest in energy, 2The first shell (1) is lowest in energy, 2ndnd level level

next and so on next and so on 1<2<3<41<2<3<4

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Maximum # of electrons in any electron shell = 2nMaximum # of electrons in any electron shell = 2n22

n =1n =1 2(2(11))22 = = 2 2

n =2n =2 2(2(22))22 == 8 8

n =3n =3 2(2(33))22 == 1818NOTE: Electrons generally fill into shells with NOTE: Electrons generally fill into shells with smallest n first; however, the filling order gets more smallest n first; however, the filling order gets more complicated after Argon (element 18).complicated after Argon (element 18).

Last Time: Number of Electrons Last Time: Number of Electrons

For the first 20 electrons:For the first 20 electrons:ShellShell 11 22 33 44

2e2e 8e8e 8e8e 2e2e

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Orbitals: “Locations” of the ElectronsOrbitals: “Locations” of the Electrons• 3-D spaces around a nucleus where an 3-D spaces around a nucleus where an

electron is most likely to be found. electron is most likely to be found.

• have shapes that represent electron density have shapes that represent electron density ((not a path the electron followsnot a path the electron follows).).

• differentdifferent shapes have shapes have differentdifferent energy energy

• each orbital can hold up to 2 electrons.each orbital can hold up to 2 electrons.

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Subshells of OrbitalsSubshells of Orbitals

Energy sublevels within principal energy Energy sublevels within principal energy

level (n)level (n)

All electrons in a subshell have the same All electrons in a subshell have the same

energyenergy

Designated Designated s, p, d, f .. s, p, d, f ..

Sublevel energy: s<p<d<fSublevel energy: s<p<d<f

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Electrons AllowedElectrons Allowed

Electrons in Electrons in samesame sublevel have sublevel have samesame energy. energy. All 2s electrons have the same energy. All 2p All 2s electrons have the same energy. All 2p

electrons have the same energy which is slightly electrons have the same energy which is slightly higher than the energy of the 2s electronshigher than the energy of the 2s electrons

s sublevel s sublevel 22 electrons electrons

p sublevel p sublevel 66 electrons electrons

d sublevel d sublevel 1010 electrons electrons

f sublevel f sublevel 1414 electrons electrons

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Electrons in Energy Levels Electrons in Energy Levels nn = 1- 4 = 1- 4

Energy Orbitals Maximum Energy Orbitals Maximum Total Total Level Level No. of Electrons No. of Electrons ElectronsElectrons11 1 1ss 2 2 22

22 2 2ss 2 2 88

22pp 6 633 3 3ss 2 2 1818

33pp 6 6 33dd 1010

44 4 4ss 2 2 3232

44pp 6 6 44dd 1010

44ff 1414

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Organization of the Periodic TableOrganization of the Periodic Table

ss11 s s22 p p11 p p2 2 pp3 3 pp44 p p55 p p66

dd11 - d - d1010

f1 - f14

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Periodic LawPeriodic Law

All the elements in a group have the same All the elements in a group have the same electron configuration in their outermost shellselectron configuration in their outermost shells

Outermost electrons are called Outermost electrons are called valence electronsvalence electrons

Elements with same # of valence electrons Elements with same # of valence electrons display similar chemical & physical properties!!!display similar chemical & physical properties!!!

Example: Example: Group 2Group 2

BeBe 2, 2, 22

Mg 2, 8, Mg 2, 8, 22

Ca Ca 2, 2, 8, 2, 2, 8, 22

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Groups and PeriodsGroups and Periods

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Periodic TablePeriodic Table

Note: Two methods for numbering; we will use Note: Two methods for numbering; we will use 1A, 2A, etc.1A, 2A, etc.

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Metals, Nonmetals, and MetalloidsMetals, Nonmetals, and Metalloids

The heavy zigzag line The heavy zigzag line separates metals and separates metals and nonmetals.nonmetals.• MetalsMetals are located to are located to

the left.the left.• NonmetalsNonmetals are located are located

to the right. to the right. • MetalloidsMetalloids are located are located

along the heavy along the heavy zigzag line between zigzag line between the metals and the metals and nonmetals.nonmetals.

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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MetalsMetals • shiny and ductileshiny and ductile• good conductors of heat and electricitygood conductors of heat and electricity

NonmetalsNonmetals• dull, brittle, and poor conductorsdull, brittle, and poor conductors• good insulatorsgood insulators

MetalloidsMetalloids• better conductors than nonmetals, but not as better conductors than nonmetals, but not as

good as metalsgood as metals• used as semiconductors and insulatorsused as semiconductors and insulators

Metals, Nonmetals, & MetalloidsMetals, Nonmetals, & Metalloids

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More Periodic TrendsMore Periodic Trends

How Atomic Orbital filling affects:How Atomic Orbital filling affects:� Atomic Size (Radius)Atomic Size (Radius)� Ionization Energy Ionization Energy

� Definitions….Definitions….

� Ionization Energy : Cost of removing an eIonization Energy : Cost of removing an e -- from a neutral atomfrom a neutral atom

Atomic Radii: Distance between center of Atomic Radii: Distance between center of nucleus and outer electron shellnucleus and outer electron shell

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Atomic Radius Within A GroupAtomic Radius Within A Group

Atomic radius Atomic radius increasesincreases going down each group going down each group of representative of representative elements.elements.


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Atomic Radius Across a PeriodAtomic Radius Across a Period

Going across a period left to right, Going across a period left to right, • an increase in number of protons increases attraction for an increase in number of protons increases attraction for

valence electrons.valence electrons.• atomic radius atomic radius decreasesdecreases..


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Ionization Energy In a GroupIonization Energy In a Group

Going up a group ofGoing up a group ofrepresentative elements,representative elements,• the distance decreases the distance decreases

between nucleus and between nucleus and valence electrons.valence electrons.

• the ionization energy the ionization energy increases.increases.


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Ionization EnergyIonization Energy

• Metals have Metals have lower lower ionization ionization energies.energies.

• Nonmetals Nonmetals have higher have higher ionization ionization energiesenergies. .


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Chapter 4!Chapter 4!

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30 Good Practice Problems (Ch 4)30 Good Practice Problems (Ch 4)

11 22 33 44 55

4.01, 4.05, 4.07, 4.09, 4.11, 4.13, 4.01, 4.05, 4.07, 4.09, 4.11, 4.13, 4.15, 4.17, 4.23, 4.25, 4.35, 4.37, 4.15, 4.17, 4.23, 4.25, 4.35, 4.37, 4.41, 4.45, 4.47, 4.49, 4.53, 4.55, 4.41, 4.45, 4.47, 4.49, 4.53, 4.55, 4.57, 4.59, 4.63, 4.65, 4.67, 4.69, 4.57, 4.59, 4.63, 4.65, 4.67, 4.69, 4.85, 4.87, 4.93, 4.97, 4.103, and 4.85, 4.87, 4.93, 4.97, 4.103, and 4.1054.105

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Chemical BondsChemical Bonds

Attraction between two or more atomsAttraction between two or more atomsInteraction between valence electronsInteraction between valence electronsIonic bondsIonic bondsCovalent bondsCovalent bonds

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An amazing thing about the universe - It works in a way that sometimes when things come together, they stick…

• Protons and neutrons in a atomic nuclei

• Atoms in molecules

H H

H H

Bonding OverviewBonding Overview

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TWO EXTREME CASESTWO EXTREME CASES• Ionic bonding:Ionic bonding: results when “Atom A” results when “Atom A” transferstransfers an an

electron to “Atom B” (e.g. salts such as NaCl)electron to “Atom B” (e.g. salts such as NaCl)

• Covalent bonding:Covalent bonding: results when atoms results when atoms shareshare electronselectrons

• Polar-covalent bonding:Polar-covalent bonding: everything in between (a everything in between (a good portion of ‘reality’)good portion of ‘reality’)

Chemical Bonds:Chemical Bonds: attractive force holding attractive force holding two or more atoms togethertwo or more atoms together

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Guiding Principle: The Octet RuleGuiding Principle: The Octet Rule

An octet in the outer shell makes atoms stableAn octet in the outer shell makes atoms stable

Electrons are Electrons are lost, gained or sharedlost, gained or shared to form an to form an

octetoctet

Electronegativity – how tightly does an atom tend to Electronegativity – how tightly does an atom tend to

hold on to electrons?hold on to electrons?

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Reminder: Valence ElectronsReminder: Valence Electrons

Electrons in the Electrons in the highest (outer)highest (outer) electron level electron level

Have most contact with other atoms Have most contact with other atoms

Known as Known as valencevalence electrons electrons

Outer shells of noble gases contain Outer shells of noble gases contain 8 valence 8 valence

electronselectrons (except He = 2)(except He = 2)

ExampleExample: : Ne Ne 2, 2, 88

ArAr 2, 8, 2, 8, 88

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Electron Dot StructuresElectron Dot Structures

Symbols of atoms with dots to represent the valence-Symbols of atoms with dots to represent the valence-shell electrons shell electrons

1A 2A 3A 4A 5A 6A 7A 8A1A 2A 3A 4A 5A 6A 7A 8A

HH•• He: He: •• •• •• •• •• •• •• •• •• •• ••

LiLi•• BeBe•• •• B B •• •• C C •• •• N N •• •• O O •• :: F F •• ::Ne Ne :: •• •• •• •• •• •• •• ••

•• •• •• •• •• •• •• •• •• •• ••

NaNa•• Mg Mg•• •• Al Al•• •• SiSi •• ••PP•• ••SS•• ::Cl Cl •• ::Ar Ar :: •• •• •• •• •• •• •• ••

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XX:: would be the electron dot would be the electron dot formula for:formula for:

1.1. NaNa

2.2. MgMg

3.3. AlAl

11 22 33 44 55

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would be the electron dot would be the electron dot formula for:formula for:

1.1. BB

2.2. CC

3.3. NN

XX

11 22 33 44 55

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