Unit 2: Electrons and Bonding
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(2) Chapter 6: Electronic Structure of Atoms. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(3) Chapter 7: Periodic Properties of the Elements. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(4) Chapter 8: Basic Concepts of Chemical Bonding. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(5) Chapter 9: Molecular Geometry and Bonding Theories. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(6) Lecture Presentation. Chapter 6 Electronic Structure of Atoms. © 2012 Pearson Education, Inc.. John D. Bookstaver St. Charles Community College Cottleville, MO.
(7) Waves. • The distance between corresponding points on adjacent waves is the wavelength ().. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(8) Waves • The number of waves passing a given point per unit of time is the frequency ().. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(9) Thursday, October 17th Entry Task(s) •Please help me put the tables back •New Seats! – Pick a new table – Pick (at least) 2 new tablemates. Agenda 1.Entry Task(s) 2. Nuts & Bolts 3. Photoelectron Spectroscopy 4. Wrap Up. •Take out HW Electronic Structure of Atoms.
(10) Electromagnetic Radiation. • All electromagnetic radiation travels at the same velocity: the speed of light (c), 3.00 108 m/s. • c = © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(11) The Nature of Energy • Energy of light is proportional to its frequency E = h where h is Planck’s constant, 6.626 10−34 J-s.. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(12) Photoelectric Effect • Photons give electrons enough energy to ‘escape’ from nucleus • The weaker the attraction, the less energy (longer wavelength) required • Explanation of photoelectric effect earned Einstein the Nobel Prize © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(13) Photoemission Spectroscopy Photoemission Spectroscopy (PES): • Based on the Photoelectric effect • Measures the amount of energy it takes to make photoelectrons • Reveals electron energy levels Electronic http://www.chem.arizona.edu/chemt/Flash/photoelectron.htmlStructure of Atoms © 2012 Pearson Education, Inc..
(14) Monday, October 15th Entry Task(s) •On whiteboard. Agenda 1. Entry Task(s) 2. Nuts & Bolts 3. Mole Day planning! 4. Finish chapter 6? 5. Wrap Up. Electronic Structure of Atoms.
(15) 6.3 Line Spectra and the Bohr Model Guiding Question: •What do light spectra reveal about electron energy levels?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(16) The Nature of Energy When given energy (heat or electricity), different elements produce light of difference colors. – Why???. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(17) The Nature of Energy • Electrons can only occupy specific energy levels • Transitions between levels will only occur at specific energy levels: – Atoms absorb light at these wavelengths (electrons go up energy levels) – Atoms emit light at these wavelengths (electrons go down energy level) Electronic © 2012 Pearson Education, Inc.. Structure of Atoms.
(18) The Nature of Energy • “White light” produces a continuous spectrum (rainbow). • Element tubes produce line spectra – Only discrete (specific) wavelengths. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(19) 6.5 Quantum Mechanics and Atomic Orbitals Guiding Questions: •How did the Uncertainty Principle lead to the idea of electron orbitals? •What are electron shells and subshells?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(20) Quantum Mechanics Quantum Mechanics: •Considers both wave and particle nature of matter •Orbitals are where electrons are likely to be •Erwin Schrödinger developed the math. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(21) Energy Level (Shell) • Main energy level (shell, n). Examples: – 1st level (1s) – 2nd level (2s & 2 p) – 3rd level (3s, 3p & 3d). © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(22) Subshells (orbital shape, l) Subshell (Shape). Number of Orbitals. s. 1. p. 3. d. 5. f. 7. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(23) 6.6 Representations of Orbitals Guiding Questions: •What are the shapes of the s, p and d subshells? •How do the shapes of the subshells maximize attraction between electrons and the nucleus?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(24) s Orbitals. • They are spherical in shape. • The radius of the sphere increases with the value of n.. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(25) s Orbitals. • “Nodes” are regions where there is 0 probability of finding an electron.. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(26) p Orbitals • They have two lobes with a node between them.. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(27) d Orbitals • Four of the five d orbitals have 4 lobes • The other resembles a p orbital with a doughnut around the center.. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(28) Tuesday, October 22nd Entry Task(s) •Write your contribution for Mole Day on the board •In the hydrogen spectrum, the red line (656 nm) is caused by a 3 2 energy level transition. The teal line (486 nm) is caused by a 4 2 energy level transition. – How much energy is released in a 4 3 transition? – What type of EMR would be released?. Electronic Structure of Atoms.
(29) Tuesday, October 22nd Agenda 1. Entry Task(s) 2. Nuts & Bolts 3. Finish chapter 6 4. Wrap Up. Electronic Structure of Atoms.
(30) 6.7 Many Electron Atoms Guiding Questions: •What is the proper order for adding electrons to orbitals? •How is the concept of electron spin to related to the Pauli Exclusion Principle? HW: #62-65 © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(31) Energies of Orbitals • Degenerate refers to electrons that have the same amount of energy • Subshells have different amount of energy: – Ex: 2p > 2s. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(32) Electron Spin • In the 1920s, it was discovered that two electrons in the same orbital are not exactly the same. • The “spin” of an electron describes its magnetic field, which affects its energy. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(33) Electron Spin • Electrons spin in opposite directions • When charged objects rotate, they create magnetic fields • If unpaired electrons in all atoms point in the same direction, a substance is magnetic! © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(34) 6.8 Electron Configurations Guiding Questions: •How should you apply Hund’s Rule to orbital filling diagrams? •How can you shorten electron configurations?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(35) Orbital Diagrams • Each box in the diagram represents one orbital. • Half-arrows represent the electrons. • The direction of the arrow represents the relative spin of the electron. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(36) Hund’s Rule “For degenerate orbitals, the lowest energy is attained when the number of electrons with the same spin is maximized.”. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(37) Periodic Table • We fill orbitals in increasing order of energy. • Different blocks on the periodic table (shaded in different colors in this chart) correspond to different types of orbitals.. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(38) 6.4 The Wave Behavior of Matter Guiding Question: •What is Heisenberg’s Uncertainty Principle?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(39) The Wave Nature of Matter • Max Planck realized that light had matter-like properties. – He referred to the particles of light as photons. • Louis de Broglie proposed the converse: – Matter should exhibit wave properties.. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(40) The Wave Nature of Matter • Louis de Broglie discovered the relationship between the mass, velocity and wavelength of a particle – h is Planck’s constant. h = mv © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(41) The Uncertainty Principle Heisenberg expanded upon this idea with his Uncertainty Principle: x is uncertainty in a particle’s position v is uncertainty in a particle’s velocity. (x) (mv) . h 4. Electronic Structure of Atoms.
(42) The Uncertainty Principle In many cases, our uncertainty of the whereabouts of an electron is greater than the size of the atom itself!. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(43) Wrap Up Thinking about today’s class, what were: •Our goals? •Key Ideas? •New Understanding? •Lingering Questions? How would you summarize our learning?. Today’s Homework •Read Chapter 7 Electronic Structure of Atoms.
(44) Thursday, October 24th Entry Task(s) On your own, write the answers to the following questions: •What are the trends for atomic radius on the periodic table: – From left to right? – From top to bottom?. Agenda 1. Entry Task(s) 2. Atomic radius 3. Effective Nuclear Charge 4.Wrap Up. •What are the effects on atomic size of: – Forming an anion? Why? – Forming a cation? Why? Electronic Structure of Atoms.
(45) Lecture Presentation. Chapter 7 Periodic Properties of the Elements. John D. Bookstaver Electronic Structure St. Charles Community College of Atoms Cottleville, MO.
(46) Periodic Trends • In this chapter, we discuss trends in: – Sizes of atoms and ions. – Ionization energy. – Electron affinity.. Electronic Structure of Atoms.
(47) 7.2 Effective Nuclear Charge Guiding Question: •What is “effective nuclear charge?”. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(48) Effective Nuclear Charge • In a many-electron atom, electrons are both attracted to the nucleus and repelled by other electrons. • The nuclear charge that an electron experiences depends on both factors. Electronic Structure of Atoms.
(49) Effective Nuclear Charge The effective nuclear charge, Zeff, is found this way: Zeff = Z − S where Z is the atomic number and S is a screening constant, usually close to the number of inner electrons. Electronic Structure of Atoms.
(50) Electronic Structure of Atoms.
(51) 7.3 Size of Atoms and Ions Guiding Questions: •How does effective nuclear charge influence atomic size? •How do the sizes of ions compare with their parent atoms?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(52) What Is the Size of an Atom? The bonding atomic radius is defined as one-half of the distance between covalently bonded nuclei.. Electronic Structure of Atoms.
(53) Sizes of Atoms The bonding atomic radius tends to — Decrease from left to right across a row (due to increasing Zeff).. — Increase from top to bottom of a column (due to the increasing value of n). Electronic Structure of Atoms.
(54) Sizes of Ions • What are the trends for neutral atoms? • Why are anions larger than their parent atoms? • Why are cations smaller than their parent atoms?. Electronic Structure of Atoms.
(55) Sizes of Ions. • In an isoelectronic series, ions have the same number of electrons. • What is the trend in atomic radius in an isoelectronic series?. Electronic Structure of Atoms.
(56) 7.4 Ionization Energy Guiding Questions: •What are the trends in the periodic table for the first ionization energy? •When will there be a big jump in ionization energy?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(57) Ionization Energy • The ionization energy is the amount of energy required to remove an electron – 1st ionization energy = the energy to create a +1 ion – 2nd ionization energy = the energy to create a +2 ion (from the +1 ion) – Etc. Electronic Structure of Atoms.
(58) Trends in First Ionization Energies. • Trends in atomic radius generally explain trends in Electronic Structure 1st ionization energy of Atoms.
(59) Trends in First Ionization Energies. • There are two notable exceptions: – Moving to group 3A – Moving to group 6A. Electronic Structure of Atoms.
(60) Trends in First Ionization Energies. • Think about the last electron that was added to Electronic Structure each group. Where did they go? of Atoms.
(61) Friday, October 25th Entry Task(s) Look at the table of ionization energy on p. 259 •What do I1, I2, I3, etc. mean? •Why does the ionization energy increase as the charge becomes more positive? •Why is there a huge jump in ionization energies at the blue line?. Agenda 1. Entry Task(s) 2. Electron Affinity 3. Properties of metals & non-metals 4.Wrap Up. Electronic Structure of Atoms.
(62) Ionization Energy • In general, removing each extra electron takes more energy • Sometimes, when moving from left to right there is a huge jump in I.E. !. Electronic Structure of Atoms.
(63) 7.5 Electrons Affinities Guiding Questions?: •What is electron affinity? •What are the trends in electron affinities?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(64) Electron Affinity In general, does it take or release energy when electrons are added to atoms? Cl + e− Cl−. Electronic Structure of Atoms.
(65) Trends in Electron Affinity Negative electron affinities mean energy is release (an exothermic process has occurred).. Electronic Structure of Atoms.
(66) Trends in Electron Affinity Why are electron affinities positive (endothermic) for: • Group 2A? • Group 8A? • Hint: where would the extra electron go? Electronic Structure of Atoms.
(67) 7.6 Metals, Nonmetals, and Metalloids Guiding Question: •What are the properties of metals, metalloids (a.k.a. semi-metals) and nonmetals?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(68) Properties of Metal, Nonmetals, and Metalloids. Electronic Structure of Atoms.
(69) Metals versus Nonmetals. Differences between metals and nonmetals tend to revolve around these properties.. Electronic Structure of Atoms.
(70) Metals versus Nonmetals • Metals tend to form cations. • Nonmetals tend to form anions.. Electronic Structure of Atoms.
(71) Metals Metals tend to be lustrous, malleable, ductile, and good conductors of heat and electricity.. Electronic Structure of Atoms.
(72) Metals • Compounds formed between metals and nonmetals tend to be ionic. • Metal oxides tend to be basic.. Electronic Structure of Atoms.
(73) Nonmetals • Nonmetals are dull, brittle substances that are poor conductors of heat and electricity. • They tend to gain electrons in reactions with metals to acquire a noble-gas configuration. Electronic Structure of Atoms.
(74) Nonmetals. • Substances containing only nonmetals are molecular compounds. • Most nonmetal oxides are acidic.. Electronic Structure of Atoms.
(75) Metalloids • Metalloids have some characteristics of metals and some of nonmetals. • For instance, silicon looks shiny, but is brittle and a fairly poor conductor. Electronic Structure of Atoms.
(76) 7.7 Trends for Group 1A and Group 2A Metals Guiding Questions: •What are the properties of alkali metals? •What are the properties of alkaline earth metals?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(77) Alkali Metals • Alkali metals are soft, metallic solids. • The name comes from the Arabic word for ashes.. Electronic Structure of Atoms.
(78) Alkali Metals • They are found only in compounds in nature, not in their elemental forms. • They have low densities and melting points. • They also have low ionization energies.. Electronic Structure of Atoms.
(79) Alkali Metals. Their reactions with water are famously exothermic. Electronic Structure of Atoms.
(80) Alkali Metals • They produce bright colors when placed in a flame.. Electronic Structure of Atoms.
(81) Alkaline Earth Metals. • Alkaline earth metals have higher densities and melting points than alkali metals. • Their ionization energies are low, but not as low as those of alkali metals.. Electronic Structure of Atoms.
(82) Alkaline Earth Metals • Beryllium does not react with water, and magnesium reacts only with steam, but the other alkaline earth metals react readily with water. • Reactivity tends to increase as you go down the group. Electronic Structure of Atoms.
(83) 7.8 Trends for Selected Nonmetals Guiding Question: •What are the trends in non-metals?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(84) Group 6A. • Oxygen, sulfur, and selenium are nonmetals. • Tellurium is a metalloid. • The radioactive polonium is a metal. Electronic Structure of Atoms.
(85) Sulfur • Sulfur is a weaker oxidizer than oxygen. • The most stable allotrope is S8, a ringed molecule.. Electronic Structure of Atoms.
(86) Group VIIA: Halogens. • The halogens are prototypical nonmetals. • The name comes from the Greek words halos and gennao: “salt formers.” Electronic Structure of Atoms.
(87) Group VIIA: Halogens • They have large, negative electron affinities. – Therefore, they tend to oxidize other elements easily.. • They react directly with metals to form metal halides. • Chlorine is added to water supplies to serve as a disinfectant. Electronic Structure of Atoms.
(88) Group VIIIA: Noble Gases. • The noble gases have astronomical ionization energies. • Their electron affinities are positive. – Therefore, they are relatively unreactive.. • They are found as monatomic gases.. Electronic Structure of Atoms.
(89) Monday, October 28th Entry Task(s) •Take out the work from Friday. •Discuss your answers to #2-4 with your group. Agenda 1. Entry Task(s) 2. Nuts & Bolts 3. Lattice Energy 4. Lewis Structures 5. Wrap Up. Electronic Structure of Atoms.
(90) Unit 2 Schedule 10/28-11/1 Mon-Wed: Chapter 8 (8.1-8.7) Thur-Fri: Exp. 1 11/4-11/8 Mon-Wed: Chapter 9 (9.1-9.5) Thur-Fri: Exp. 2. 11/11-11/15 Mon: Veteran’s Day Tue-Thurs: Exp. 2 Fri: Midterm (covering Ch. 1-9). © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(91) Lecture Presentation. Chapter 8 Basic Concepts of Chemical Bonding. John D. Bookstaver Electronic Structure St. Charles Community College of Atoms Cottleville, MO.
(92) Chemical Bonds • Three basic types of bonds – Ionic • Electrostatic attraction between ions.. – Covalent • Sharing of electrons.. – Metallic • Metal atoms bonded to several other atoms. Electronic Structure of Atoms.
(93) Lewis Symbols. • Lewis structures show valence electrons. Electronic Structure of Atoms.
(94) 8.2 Ionic Bonding Guiding Question: •What is lattice energy?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(95) Energetics of Ionic Bonding As we saw in the last chapter, it takes 496 kJ/mol to remove electrons from sodium.. Electronic Structure of Atoms.
(96) Energetics of Ionic Bonding We get 349 kJ/mol back by giving electrons to chlorine.. Electronic Structure of Atoms.
(97) Energetics of Ionic Bonding But these numbers don’t explain why the reaction of sodium metal and chlorine gas to form sodium chloride is so exothermic!. Electronic Structure of Atoms.
(98) Energetics of Ionic Bonding The attraction between Na+ and Cl- produces a lot of energy!. Electronic Structure of Atoms.
(99) Lattice Energy • Lattice Energy: – The energy required to completely separate a mole of a solid ionic compound into its gaseous ions.. • Lattice Energy is an example of Coulomb’s Law, which is found below: Q1Q2 Eel = Electronic d Structure of Atoms.
(100) Lattice Energy What is the relationship between: – The magnitude of charge and lattice energy? – The distance between the ions and lattice energy?. Electronic Structure of Atoms.
(101) 8.3 Covalent Bonding Guiding Question: •How does bonding allow atoms to meet the Octet rule?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(102) Entry Task •What are the periodic trends in Electronegativity? •How is electronegativity related to effective nuclear charge?. Electronic Structure of Atoms.
(103) 8.4 Bond Polarity and Electronegativity Guiding Question: •How does electronegativity difference affect bond type?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(104) Polar Covalent Bonds. “Heat maps” show electron distribution in a molecule •Red means high electron density (i.e. negative charge) •Purple means low electron density (i.e. positive charge) Electronic Structure of Atoms.
(105) Polar Covalent Bonds • The dipole moment, , produced by two equal but opposite charges separated by a distance, r, is calculated: = Qr • It is measured in debyes (D).. Electronic Structure of Atoms.
(106) Polar Covalent Bonds • \. What seems to be more important in determining D: •Bond length? •EN difference?. Electronic Structure of Atoms.
(107) Polar Covalent Bonds • \. Calculate the partial charges (Q) on hydrogen and each halide. Electronic Structure of Atoms.
(108) 8.5 Drawing Lewis Structures Guiding Questions: •How can Lewis structures determine the existence of multiple bonds and formal charges? •Which Lewis structure is best?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(109) Lewis Structures. Lewis structures are representations of molecules showing all valence electrons Often, the correct Lewis structure can be found by forming bonds between unpaired electrons. Electronic Structure of Atoms.
(110) Lewis Structures. Draw Lewis structures for: NH3 C2H4 PF5 Electronic Structure of Atoms.
(111) Writing Lewis Structures. PCl3. 1. Find the sum of valence electrons of all atoms in the polyatomic ion or molecule.. – If it is an anion, add one electron for each negative charge. – If it is a cation, subtract one electron for each Keep track of the electrons: positive charge.. 5 + 3(7) = 26. Electronic Structure of Atoms.
(112) Writing Lewis Structures 2. The central atom is the least electronegative element that isn’t hydrogen. Connect the outer atoms to it by single bonds. Keep track of the electrons: 26 − 6 = 20. Electronic Structure of Atoms.
(113) Writing Lewis Structures 3. Fill the octets of the outer atoms.. Keep track of the electrons: 26 − 6 = 20; 20 − 18 = 2. Electronic Structure of Atoms.
(114) Writing Lewis Structures 4. Fill the octet of the central atom.. Keep track of the electrons: 26 − 6 = 20; 20 − 18 = 2; 2 − 2 = 0. Electronic Structure of Atoms.
(115) Writing Lewis Structures 5. If you run out of electrons before the central atom has an octet… …form multiple bonds until it does.. Electronic Structure of Atoms.
(116) Wednesday, October 30th Entry Task(s) •Grab a white board •Use the rules from yesterday to determine the Lewis structures of HCN and CO2 – Make sure you keep track of the # of electrons on your board!. Agenda 1.Entry Task(s) 2.Lewis Structures 3.Resonance 4.Violations of the Octet rule 5.Exp. 1 6.Wrap Up. Electronic Structure of Atoms.
(117) Writing Lewis Structures 5. If you run out of electrons before the central atom has an octet… …form multiple bonds until it does.. Electronic Structure of Atoms.
(118) Writing Lewis Structures • Then assign formal charges. – For each atom, count the electrons in lone pairs and half the electrons it shares with other atoms. – Subtract that from the number of valence electrons for that atom: the difference is its formal charge.. Electronic Structure of Atoms.
(119) Writing Lewis Structures • The best Lewis structure… – …is the one with the fewest charges. – …puts a negative charge on the most electronegative atom. Draw the best Lewis structure of NCO-. Electronic Structure of Atoms.
(120) Writing Lewis Structures • The best Lewis structure… – …is the one with the fewest charges. – …puts a negative charge on the most electronegative atom.. Electronic Structure of Atoms.
(121) 8.6 Resonance Structures Guiding Question: •What is resonance?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(122) Resonance Draw a Lewis structure for ozone, O3.. Electronic Structure of Atoms.
(123) Resonance • One Lewis structure cannot accurately depict a molecule like ozone. • We use multiple structures, resonance structures, to describe the molecule. Electronic Structure of Atoms.
(124) Resonance – Both O—O bonds are the same length. – Both outer oxygens have a charge of −1/2.. Electronic Structure of Atoms.
(125) Resonance Just as green is a synthesis of blue and yellow… …ozone is a synthesis of these two resonance structures. – Both O—O bonds are the same length. – Both outer oxygens have a charge of −1/2. Electronic Structure of Atoms.
(126) Resonance • Formate is a polyatomic ion: (HCO2)• The electrons in the Carbon-Oxygen bonds are are delocalized.. Electronic Structure of Atoms.
(127) Resonance • The organic compound benzene, C6H6, has two resonance structures. • The electrons are. Electronic Structure of Atoms.
(128) 8.7 Exceptions to the Octet Rule Guiding Question: •What are the 3 classes of exemptions to the Octet Rule?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(129) Exceptions to the Octet Rule 3 Categories of Exemptions: –Odd # of electrons –Less than an octet –More than an octet. Electronic Structure of Atoms.
(130) Odd Number of Electrons Though relatively rare and usually quite unstable and reactive, there are ions and molecules with an odd number of electrons. What is the Lewis Structure for NO?. Electronic Structure of Atoms.
(131) Fewer Than Eight Electrons. • What is the Lewis Structure for BF3? – What are the formal charges if Boron meets the Octet rule?. Electronic Structure of Atoms.
(132) Fewer Than Eight Electrons Meeting the Octet rule is less important than putting a positive formal charge on an more electronegative element. Electronic Structure of Atoms.
(133) More Than Eight Electrons • The only way PCl5 can exist is if phosphorus has 10 electrons around it.. Electronic Structure of Atoms.
(134) More Than Eight Electrons Draw Lewis Structures for the phosphate PAI:. Electronic Structure of Atoms.
(135) More Than Eight Electrons Meeting the Octet rule is less important than reducing the number of formal charges. Electronic Structure of Atoms.
(136) Monday, October 28th Entry Task(s) On your own (if possible) draw Lewis Structures for: •BeCl2 •CCl2O. Agenda 1. Entry Task(s) 2. Nuts & Bolts 3. VSEPR 5. Wrap Up. •CBr4 •SF4 •XeF4 Electronic Structure of Atoms.
(137) Lecture Presentation. Chapter 9 Molecular Geometries and Bonding Theories John D. Bookstaver Electronic Structure St. Charles Community College of Atoms Cottleville, MO.
(138) 9.1 Molecular Shapes Guiding Question: •How do the number of groups around a central atom affect its shape?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(139) Modeling the VSEPR Model • Balls of clay represent atoms. • Toothpicks represent electron domains • Create the largest angles possible between the toothpicks! • Sketch each model. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(140) 9.2 The VSEPR Model Learning Target: •How do the two types of electron groups influence molecular shape?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(141) Molecular Shapes • The shape of a molecule plays an important role in its reactivity. • By noting the number of bonding and nonbonding electron pairs, we can easily predict the shape of the molecule.. Electronic Structure of Atoms.
(142) Valence-Shell Electron-Pair Repulsion Theory (VSEPR) • Electron domains (bonds or nonbonding pairs) repel each other. • The ideal shape creates the largest possible angle between domains. Electronic Structure of Atoms.
(143) Electron Domains Double (and triple) bonds only count as a single domain. Atom A has four electron domains. Electronic Structure of Atoms.
(144) Molecular Geometries. Molecular shape names describe the structure of the bonds Electronic Structure of Atoms.
(145) Electron-Domain Geometries Table 9.1 contains the electron-domain geometries for two through six electron domains around a central atom. Electronic Structure of Atoms.
(146) Wednesday, November 6th Entry Task(s) Are the following bonds polar or non-polar? •C-O, S-O, N-F, Cl-F. Agenda 1. Entry Task(s) 2. VSEPR 3. Hybridization 4. Wrap Up. What are the shapes of the molecules below?. Electronic Structure of Atoms.
(147) Nonbonding Pairs and Bond Angle • Nonbonding pairs are physically larger than bonding pairs. • This makes the angles between the bonds slightly smaller. Electronic Structure of Atoms.
(148) Trigonal Bipyramidal Electron Domain • There are two distinct positions in this geometry: – Axial – Equatorial. Electronic Structure of Atoms.
(149) Trigonal Bipyramidal Electron Domain. Lower-energy conformations result from having nonbonding electron pairs in equatorial, rather than axial, positions in this geometry. Electronic Structure of Atoms.
(150) 9.3 Molecular Shape and Molecular Polarity Guiding Question: •How do molecular shape and bond polarity determine molecular polarity?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(151) Polarity • In Chapter 8, we discussed bond dipoles. • But just because a molecule possesses polar bonds does not mean the molecule as a whole will be polar. Electronic Structure of Atoms.
(152) Polarity By adding the individual bond dipoles, one can determine the overall dipole moment for the molecule.. Electronic Structure of Atoms.
(153) Polarity. Electronic Structure of Atoms.
(154) 9.4 Covalent Bonding and Orbital Overlap Guiding Question: •How are covalent bonds formed?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(155) Overlap and Bonding • Covalent bonds are formed when atoms share electrons • Orbitals must overlap for this to occur. Electronic Structure of Atoms.
(156) Overlap and Bonding • What determines bond length? – Attraction between each nucleus and the electrons – Repulsion between the nuclei. Electronic Structure of Atoms.
(157) 9.5 Hybrid Orbitals Learning Target: •How does hybridization of orbitals allow atoms to bond?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(158) Hybrid Orbitals Beryllium cannot bond with this electron configuration. Electronic Structure of Atoms.
(159) Hybrid Orbitals Beryllium cannot bond with this electron configuration If the Be atom absorbs energy, it can form two bonds. However, these orbitals aren’t the same, so they would bond differently. Electronic Structure of Atoms.
(160) Hybrid Orbitals. • Hybridizing creates blended orbitals. – They bond the same (as we would expect) – The hybrid orbitals came from an s and a p orbital, so they are called sp orbitals. (other possibilities are sp2 and sp3). Electronic Structure of Atoms.
(161) Hybrid Orbitals • The hybrid orbitals are identical to each other • Be has 2 electrons domains, so it is linear. Electronic Structure of Atoms.
(162) 9.6 Multiple Bonds Learning Target: •How do orbitals overlap to create multiple bonds?. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(163) Sigma () Bonds. • Sigma bonds are characterized by – Head-to-head overlap – Circular symmetry – Electrons along the axis Electronic Structure of Atoms.
(164) Pi () Bonds. • Pi bonds are characterized by – Side-to-side overlap. (requires p orbitals) – Mirror symmetry – Electrons above and below axis Electronic Structure of Atoms.
(165) Single Bonds Single bonds are always bonds, because overlap is greater, resulting in a stronger bond and more energy lowering.. Electronic Structure of Atoms.
(166) Multiple Bonds In a multiple bond, one of the bonds is a bond and the rest are bonds.. Electronic Structure of Atoms.
(167) Multiple Bonds. Carbon: •Forms 3 σ bonds and 1 bond •Has sp2 and p orbitals Oxygen: •Forms 1 σ bond and 1 bond •Has sp2 and p orbitals (non-bonding pairs are in the sp2 orbitals). Electronic Structure of Atoms.
(168) Multiple Bonds In triple bonds, as in acetylene, two sp orbitals form a bond between the carbons, and two pairs of p orbitals overlap in fashion to form the two bonds.. Electronic Structure of Atoms.
(169) Delocalized Electrons: Resonance When writing Lewis structures for species like the nitrate ion, we draw resonance structures to more accurately reflect the structure of the molecule or ion.. Electronic Structure of Atoms.
(170) Delocalized Electrons: Resonance • Resonance requires overlap of p orbitals • The -1 charge is distributed throughout the ion. Electronic Structure of Atoms.
(171) Resonance The organic molecule benzene has six bonds and a p orbital on each carbon atom.. Electronic Structure of Atoms.
(172) Resonance • In reality the electrons in benzene are not localized, but delocalized. • The even distribution of the electrons in benzene makes the molecule unusually stable.. Electronic Structure of Atoms.
(173) 9.7 & 9.8 Will not be covered •Not on AP test •College sophomore level material (organic chemistry). © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
(174) Trigonal Bipyramidal Electron Domain • There are four distinct molecular geometries in this domain: – – – –. Trigonal bipyramidal Seesaw T-shaped Linear Electronic Structure of Atoms.
(175) Octahedral Electron Domain • All positions are equivalent in the octahedral domain. • There are three molecular geometries: – Octahedral – Square pyramidal – Square planar Electronic Structure of Atoms.
(176) Warm-Up For each Electrons & Bonding (E&B) standards below: •Write down the sections in the book that relate to the standard (hint: they’re in chapters 6-9) •Rate yourself on a scale of 1-5 E&B 2: Choose the right wavelength of light for spectroscopy & photochemical reactions and explain photoelectric effect E&B 3: Use effective nuclear charge to explain periodic properties of the atom E&B 4: Draw Lewis structures for molecules with formal charges and violations of the octet rule E&B 5: Use VSEPR theory to precisely determine bond geometry. © 2012 Pearson Education, Inc.. Electronic Structure of Atoms.
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