Post on 25-Dec-2015
transcript
Section 12.4
Structure of Molecules
B. Ionic bonding and Structures of Ionic Compounds
• Polyatomic ions work in the same way as simple ions– The covalent bonds hold the polyatomic ion together so it
behaves as a unit
Ionic Compounds Containing Polyatomic Ions
Section 12.4
Structure of Molecules
• Writing Lewis Structures for Polyatomic Ions
Section 12.4
Structure of Molecules
[SO4]2-
2-
Section 12.4
Structure of Molecules
[NO2]-
-
Section 12.4
Structure of Molecules
[NH4]+
+
Section 12.4
Structure of Molecules
1. SWBAT understand molecular structure, be able to predict molecular geometry from the number of electron pairs and to apply the VSEPR model to molecules with double bonds in a virtual laboratory.
Objectives
Section 12.4
Structure of Molecules
A. Molecular Structure
• The atoms in a molecule have a three dimensional arrangement,– Water - bent
LQHS
Section 12.4
Structure of Molecules
A. Molecular Structure
• Linear structure – atoms in a line
– Carbon dioxide
Section 12.4
Structure of Molecules
A. Molecular Structure
• Trigonal planar – atoms in a triangle
– BF3
Section 12.4
Structure of Molecules
A. Molecular Structure
• Tetrahedral structure
– Methane CH4
Section 12.4
Structure of Molecules
B. The VSEPR Model
• Valence shell electron pair repulsion (VSEPR) model – Molecular structure is determined by minimizing
repulsions between electron pairs
Section 12.4
Structure of Molecules
B. The VSEPR Model
– 180o - linear – (Note, this is an ionic compound exception AND an octet
rule exception!)
Two Pairs of Electrons
• BeCl2
Section 12.4
Structure of Molecules
B. The VSEPR Model
– 120o – trigonal planar
Three Pairs of Electrons
• BF3
Section 12.4
Structure of Molecules
B. The VSEPR Model
– 109.5o – tetrahedral
Four Pairs of Electrons
• CH4
Section 12.4
Structure of Molecules
B. The VSEPR Model
Section 12.4
Structure of Molecules
B. The VSEPR Model
Section 12.4
Structure of Molecules
C. Molecules with Double Bonds
When using VSEPR model to predict molecular geometry of a molecule
• a double bond is counted the same as a single electron pair
LQHSVirtual Lab