1 3D Shapes of Covalent Compounds Electron pairs around an atom repel each other. Bonding and unshared pairs of e - spread out in space to move as far.

Slides:

Advertisements

Similar presentations

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

Advertisements

BONDING Ch 8 & 9 – Honors Chemistry General Rule of Thumb:

Molecular Geometry Lewis structures show the number and type of bonds between atoms in a molecule. –All atoms are drawn in the same plane (the paper).

Lewis Dot Structures and Molecular Geometry

General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 5.8 Shapes and Polarity of Molecules Chapter 5 Compounds and Their Bonds © 2013.

SHAPES OF MOLECULES. REMINDER ABOUT ELECTRONS  Electrons have negative charges  Negative charges “repel” each other  In molecules, electrons want to.

V alence S hell E lectron P air R epulsion Theory Planar triangular Tetrahedral Trigonal pyramidal Bent.

VSEPR Theory – Valence Shell Electron Pair Repulsion theory

Chapter 10: Structure of Solids and Liquids

Covalent Bonds The joy of sharing!.

Unit 04: BONDING IB Topics 4 & 14 Text: Ch 8 (all except sections 4,5 & 8) Ch 9.1 & 9.5 Ch My Name is Bond. Chemical Bond.

Lecture 23 © slg CHM 151 TOPICS : 1. Molecular Shapes 2. Polyatomic ion Shapes 3. Introduction to Bond Polarity.

1 New subject... Why does stuff stick together? In covalent bonds electrons are not always shared “equally.” Some nuclei have a stronger pull for electrons.

Chapter 10 Properties of Solids and Liquids

Polar vs. Non Polar Molecules. Covalent/Molecular Compounds All molecular compounds are either polar or nonpolar.

Chapter 4 Compounds and Their Bonds

POLAR BONDS AND MOLECULES Ms. Withrow November 10, 2008.

Chapter 16 Notes, part IV Polarity and IMFs. Types of Bonds Up until now, we have assumed that there are two types of bonds: Covalent and Ionic. This.

BONDING General Rule of Thumb: metal + nonmetal = ionic

1 Electronegativity? The ability of an atom in a molecule to attract shared electrons to itself. The ability of an atom in a molecule to attract shared.

Polarity and IMF. Polar Bonds When the atoms in a bond are the same, the electrons are shared equally. This is a nonpolar covalent bond. When two different.

2008, Prentice Hall Chemistry: A Molecular Approach, 1 st Ed. Nivaldo Tro Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA.

Chapter 8 Molecular Structure, Valence Bond Theory, and Hybridization.

Chapter 4 Covalent Compounds.

Molecular Shape and Polarity The Importance of Geometry in Determining Physical Properties.

Intermolecular and Intramolecular Forces Review. In the compound PCl 3, how many valence electrons are present?

Molecular Shape and Polarity The Importance of Geometry in Determining Physical Properties.

POLARITY AND SOLUBILITY: “Like dissolves like”. Review of shapes: What are the five basic shapes?  Linear  Trigonal Planar  Tetrahedral  Trigonal.

 chemical bond - force that holds groups of atoms together  group function as a unit  bond NRG – NRG required to break bond  indicates strength of.

Covalent Compounds Chapter Covalent Bonds. Covalent Bond The sharing of electrons between atoms Forms a molecule To have stable (filled) orbitals.

LEWIS STRUCTURES & MOLCULAR GEOMETRY. TYPES OF COVALENT BONDS SINGLE BONDS LONGEST OF THE 3 TYPES WEAKEST OF THE 3 TYPES CONTAINS ONE PAIR OF ELECTRONS.

 no simple, and yet complete, way to define this  forces that hold groups of atoms together and make them function as a unit  a bond will form if the.

Valence Shell Electron Pair Repulsion Theory –Electron pairs orient themselves in order to minimize repulsive forces.

Drawing covalent bonds Draw the following covalent compounds in your notebooks now: NH3 CH4 CO2 Draw the following covalent compounds in your notebooks.

VSEPR Theory. Molecular Structure Molecular structure – the three- dimensional arrangement of atoms in a molecule.

Chemical Bonding b Chapter 6. Chemical bond b The force (electrical attraction) that binds two atoms together.

Topic 1Topic 2Topic 3Topic 4Topic

Chapter 8 “Covalent Bonding” Part 3 Ball-and-stick model.

COVALENT BONDING.

Unit 11 - Bonding Types of Chemical Bonds Electronegativity Bond Polarity and Dipole Moments Stable Electron Configurations Lewis Structures Lewis Structures.

Molecular Compounds Polarity.

Chapter 6 The Shape of Molecules.

CHAPTER OUTLINE Electronegativity Polarity & Electronegativity

Polarity of Molecules 301 Chemistry.

Chapter 12 Chemical Bonding.

6.8 Shapes and Polarity of Molecules

Chapter 6 The Shape of Molecules.

Chapter 10 Properties of Solids and Liquids

Valence Shell Electron Pair Repulsion Theory

Chapter 10 Chemical Bonding II

Chapter 10 Chemical Bonding II

Drawing Molecules and Shapes

Bond polarity vs. Molecule polarity

3.2 VSEPR Theory. 3.2 VSEPR Theory VSEPR Theory Valence Shell Electron Pair Repulsion Predicts the 3-D geometry of molecules (covalent compounds) The.

Real Molecule Shapes Any molecule containing only 2 atoms has a linear shape. To predict shapes of molecules with more than 2 atoms we use VESPR theory.

My Name is Bond. Chemical Bond

GEOMETRY AND POLARITY OF MOLECULES

Drawing Lewis Structures

Drawing Molecules and Shapes

Types of Covalent Bonds

Nonpolar Covalent Bonds

Although all covalent bonds involve a sharing of one or more pairs of electrons between bonding atoms, most of the time this sharing is not equal. One.

Recall: Electronegativity

Molecular Structure and Shape

POLAR COVALENT BONDS COVALENT= 2 NONMETALS

Nonpolar Covalent Bonds

Drawing Molecules and Shapes

Drawing Molecules and Shapes

Presentation transcript:

1 3D Shapes of Covalent Compounds Electron pairs around an atom repel each other. Bonding and unshared pairs of e - spread out in space to move as far apart as possible. Any bonded atoms move with the electron pairs.

2 So, to ask “What is the shape of a compound?” means we first must ask (and answer): What is the arrangement of the electron pairs around an atom? “What is the arrangement of the electron pairs around an atom?” two electron pairs two electron pairs Z 180° linear arrangement maximum separation = 180° = linear arrangement

3 three e - pairs Z 120° trigonal planar maximum separation = 120° = trigonal planar arrangement

4 four e - pairs Z maximum separation in 3D = 109° tetrahedral 109° = tetrahedral arrangement.

5 ifnumber of groups = number of electron pairs Result & Conclusion... if the number of groups connected to an atom = number of electron pairs on the atom, thengeometry of the molecule = geometry of the electron pairs then the geometry of the molecule around that atom = geometry of the electron pairs around the atom.

6 Examples H-Be-H H-Be-H 2e - pairs = linear; 2 bonded atoms = linear molecule. BCl 3 3e - pairs = trigonal planar; 3 bonded atoms = trig planar molecule

7 CHHH H 4e - pairs around C = tetrahedral, 109°; 4 bonded atoms around C = tetrahedral molecule, 109° bond angles

8 Perspective Rendering CH 4 : CH H H H = bond in plane of page = bond back plane of page = bond projects out at viewer

9 What if #e - pairs doesn’t = # bonded atoms?? N H H H 4 e - pairs around N; max separation at 109° = tetrahedral There are only 3 H atoms connected to the e - pairs: shape of molecule describes mass points in space. So...

10 three H atoms lie in one plane with the N atom above trigonal pyramidal What we see in space are the heavy mass points-- the nuclei of the atoms arranged around the N. The three H atoms lie in one plane (making a triangle), with the N atom above, like the apex of a pyramide. The molecular shape is said to be trigonal pyramidal.

11 Consider H 2 O H O H Around Oxygen: 4e- pairs, arranged tetrahedrally. bentV- shaped # of Atoms connected to O = 2. Molecular shape appears bent or V- shaped: O about 109° H H

12 Shapes of Compounds with multiple bonds Formaldehyde, HCHO is H - C = O H - C = O 4e - pairs on C => H BUT they must point in the same general direction in space H BUT 2 pairs are in a double bond ===> they must point in the same general direction in space...

13 the C=O e - pairs are considered as 1 pair for geometry purposes. Thus: the C=O e - pairs are considered as 1 pair for geometry purposes. it seems there are only 3 e - pairs around C, and no unshared pairs. So: it seems there are only 3 e - pairs around C, and no unshared pairs. shape of molecule around O is. Result: shape of molecule around O is trigonal planar.

14 Make predictions for... * Ethylene, C 2 H 4, or H - C = C - H H H * Acetylene, C 2 H 2, or H - C C - H

15 New subject... Covalent Bonds - all sharing isn’t equal Some nuclei have a stronger pull for electrons than others. Electronegativity Electronegativity describes the relative strength of attraction an atom has for e -.

16 Metalslow electronegativity Metals have very low electronegativity values -- they give up e - easily. Non-metalslarger electronegativity Non-metals have larger electronegativity values -- they attract e -. across a periodgoing up a Group or column. Electronegativity increases: across a period, & going up a Group or column.

17 Most electronegative element = Fluorine (F). Least Electronegative = Cesium (Cs)/Francium (Fr). Pauling electronegativity scale uses rating. Most electronegative = 4 Not electronegative = 0

18 When two non-metals form a covalent bond, the e - pair may not be evenly shared between the two nuclei. If one element is more electronegative than the other, the e - pair is pulled closer to that nucleus.

19 Example Cl is more EN than H: H - ClCl is more EN than H: the electron pair in the bond is pulled closer to Cl. The H-Cl bond is a polar covalent bond, shown as: The H-Cl bond is a polar covalent bond, shown as:  + H-Cl   The symbol  + or  - means “partial - charge.”

20 A polar covalent bond has a “dipole.” (+ and - ends) Molecules may have more than one polar covalent bond. Water, H 2 O has two O-H bonds each having a dipole as  + H - O  -. The entire molecule may be polar...

21 if the molecular geometry creates an over-all net dipole moment: O  - net  + H H  + Water can solvate ions because it has polarity. (More on this later.)

22 A molecule with polar bonds may be non-polar overall if the individual dipoles cancel: Cl CCl 4 is Cl - C - Cl Cl Each C-Cl bond is polar as  + C-Cl  -.

23 But each C-Cl bond points away in space by 109° in opposite directions: there is no net dipole moment for CCl 4. We say it is a non-polar molecule.