1 Announcements Announcements & Agenda & Agenda (01/24/07) (01/24/07) You should currently be reading Ch You should currently be reading Ch 4! 4! Quiz over Ch 3 moved to Friday! Quiz over Ch 3 moved to Friday! Pick up Graded Quizzes if you Pick up Graded Quizzes if you haven’t haven’t Welcome Visitors! Welcome Visitors! Today: Today: Recap of Mon: Electron Energy Recap of Mon: Electron Energy Levels (3.7) Levels (3.7) Periodic trends (3.3, 3.8) Periodic trends (3.3, 3.8) Start Ch 4 (Finally!) Start Ch 4 (Finally!)
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
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 2222 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
1111
Organization of the Periodic TableOrganization of the Periodic Table
ss11 s s22 p p11 p p2 2 pp3 3 pp44 p p55
pp66
dd11 - d - d1010
f1 - f14
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Periodic LawPeriodic Law
All the elements in a group have the same electron All the elements in a group have the same electron configuration in their outermost shellsconfiguration in their outermost shells
Outermost electrons are called Outermost electrons are called valence electronsvalence electrons
Elements with same # of valence electrons display Elements with same # of valence electrons display similar chemical & physical properties!!!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.
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
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
