Molecular Polarity Individual bonds tend to be polar, but that doesn’t mean that a molecule will be polar overall. To determine molecular polarity, you.

Slides:



Advertisements
Similar presentations
Molecular Shape VSEPR (Valence Shell Electron Pair Repulsion) Theory.
Advertisements

Covalent Bonds All atoms want an octet (Octet Rule) –Can share valence e-s e-s occupy molecular orbitals Where are e-s located? –Attraction and repulsion.
1 Drawing Lewis Structures A step-by-step guide See page 305.
Covalent Bonding Sec. 8.3: Molecular Structures. Objectives List the basic steps used in drawing Lewis structures. List the basic steps used in drawing.
Lewis Diagrams.
Chapter 7-2 Covalent Bonding.
I Chemical Bonding. Chemical Bond  attractive force between atoms or ions that binds them together as a unit  bonds form in order to…  decrease potential.
Bond Polarity covalent bonding between unlike atoms results in unequal sharing of the electrons one atom pulls the electrons in the bond closer to its.
Honors Chemistry Lewis Structures and VSEPR Theory.
1 Resonance and Formal Charge. 2 Resonance and Formal Charge: At the conclusion of our time together, you should be able to: 1. Define resonance 2. Determine.
1 Molecular Geometry and Polarity Part B: Lewis Structure Dr. Chin Chu River Dell Regional High School.
1 Resonance and Formal Charge. 2 SAMPLE PROBLEM:Writing Resonance Structures PLAN: SOLUTION: PROBLEM:Write resonance structures for the nitrate ion, NO.
Variations in Lewis Structures. Resonance Forms  Some substances are not adequately defined by a single Lewis Structure  For example, ozone ( O 3 ),
Writing Lewis Structures of Simple Covalent Molecules
Covalent bonds can be depicted by straight lines.
AP Chapter 7 Covalent Bonding Lewis Structures A Lewis structure shows the distribution of outer (valence) electrons in an atom, molecule, or polyatomic.
IIIIII I. Lewis Diagrams Ch. 9 – Molecular Structure C. Johannesson.
What happens when a molecule does not seem to have enough valence electrons?  Main goal is to satisfy octet rule for every atom in chemical compound.
What is polarity?  Focus on covalent bonds  Contributes to the properties of chemical compounds  Based on electronegativity difference between atoms.
IIIIII I. Lewis Diagrams Molecular Structure. A. Octet Rule n Remember…  Most atoms form bonds in order to have 8 valence electrons.
Ch. 6: Chemical Bonding I: Drawing Lewis Structures and Determining Molecular Shapes Dr. Namphol Sinkaset Chem 200: General Chemistry I.
Representing Molecules Resonance Exceptions to the Octet Rule Formal Charge.
Resonance  A molecule or polyatomic ion for which 2 or more dot formulas with the same arrangement of atoms can be drawn is said to exhibit RESONANCE.
IIIIII I. Lewis Diagrams (p ) Ch. 6 – Molecular Structure.
IIIIII C. Johannesson I. Lewis Diagrams (p. 170 – 175) Ch. 6 – Molecular Structure.
Boron tends to form compounds in which the boron atom has fewer than eight electrons around it (it does not have a complete octet). BH 3 = 6e –
Electron-Dot Model of Bonding: Lewis Structures Lewis structures are drawn by following simple rules. 1.Draw the molecular skeleton 2.Count the number.
1 Resonance and Formal Charge. 2 Resonance and Formal Charge: At the conclusion of our time together, you should be able to: 1. Define resonance 2. Determine.
Covalent Compounds. Resonance Resonance structures are those that occur when it is possible to draw two or more valid electron dot structures that have.
Section 12.3 Lewis Structures 1.To learn to write Lewis structures 2.To learn to write Lewis structures for molecules with multiple bonds Objectives.
Carbon’s valence electrons?. Hybrid Orbitals  Mixing of valence shell orbitals to form new similar orbitals for bonding electrons.
Chapter 8 Bonding: General Concepts. Chapter 8 Questions to Consider  What is meant by the term “chemical bond”?  Why do atoms bond with each other.
Lewis Structures H is always a terminal atom The atom with the lowed EN is the central atom Find the total # of valence (ions add and lose electrons) Bond.
1 Slater’s Rules for the Determination of Effective Nuclear Charge (Z*) 1) Write out the electronic configuration of the element and group the orbitals.
Molecular Geometry Lewis Structures VSEPR Theory
Lewis Structure Shows how valence electrons are arranged among atoms in a molecule. Reflects central idea that stability of a compound relates to noble.
Chem Take out HW to be checked Today: Molecular Shapes Cont; IMFs
Valence Shell Electron Pair Repulsion Theory
Chapter 9 Valence Bond Theory.
Covalent bonding & Lewis Structures
Chapter 8 Covalent Bonding 8.2 The Nature of Covalent Bonding
Bonding Unit Part B) Structures and Shapes
Localized Electron Model
Unit 6 – Molecular Structure
Ch. 9 – Molecular Structure
Chapter VII.
Molecular Structure Lewis Diagrams (p. 170 – 175).
Molecular Structures Section 9.3
Exceptions to the Octet Rule
III. Molecular Polarity
Delocalized Pi Bonding
Delocalized Electrons - Resonance Structures (14.3)
Lewis Structures visualize molecular structure
7.8 NOTES Exceptions to the Octet Rule
Resonance Forms Some substances are not adequately defined by a single Lewis Structure For example, ozone ( O3) , can be drawn just as easily two different.
Ch. 6 – Molecular Structure
Lewis Structures visualize molecular structure
I. Lewis Diagrams (p. 202 – 213) Lecture 2.
Chapter 6-2 Lewis Structures.
Resonance and Formal Charge
I. Lewis Diagrams (p. 202 – 213) Lecture 2.
Ch. 6 – Molecular Structure
Lewis Structures Two dimensional pictures of covalent species that show how the atoms are joined together with covalent bonds.
10.5 (exceptions) Tro's Introductory Chemistry, Chapter 10.
7.5 NOTES Exceptions to the Octet Rule
V. Molecular Polarity (p. 183)
Covalent bonding review
III. Molecular Polarity (p. 183)
Lewis Structures visualize molecular structure
Covalent Bonding and Molecular Compounds
Presentation transcript:

Molecular Polarity Individual bonds tend to be polar, but that doesn’t mean that a molecule will be polar overall. To determine molecular polarity, you need to consider the 3-D shape and see if polarity arrows cancel or not.

Note that all these molecules have polar bonds. Two of these molecules are nonpolar because their symmetry causes the charges to cancel out: Copyright by the Glencoe Division of Macmillan/McGraw-Hill School Publishing Company

Multiple Valid Lewis Structures Sometimes more than one Lewis structure can be drawn for the same molecule. For example, ozone (O 3 ).

Resonance Forms Resonance forms are also known as resonance structures. Resonance forms have the same relative placement of atoms, but different locations of bonding and lone e- pairs.

Resonance Hybrid Neither resonance form is a true picture of the molecule. The molecule exists as a resonance hybrid, which is an average of all resonance forms. In a resonance hybrid, e- are delocalized over the entire molecule.

Important Resonance Forms If all resonance forms have the same surrounding atoms, then each contributes equally to the resonance hybrid. If this is not the case, then one or more resonance forms will dominate the resonance hybrid. How can we determine which forms will dominate?

Exceptions to the Octet Rule We’ve already discussed expanded valence cases, but there are other exceptions as well.  e- deficient atoms like Be and B, e.g. BeCl 2 and BF 3.  Compounds w/ odd # of e-’s: free radicals. Examples include NO and NO 2.  Expanded valence – when d orbitals are used to accommodate more than an octet.