11/23 Bell Work Jack Axe charges $5 to cut a wooden log into 2 pieces.  How much would he charge to cut a log into 4 pieces?

11/23 Schedule  Finish Ch 7 “Ionic Bonding” Test  Notes online “Covalent Bonding Pt. 1”  Ch 8.1 “Molecular Compounds”  Includes “Molecular Shapes” slide, use protractor if needed Assignments: 1. SR 8.1 “Molecular Compounds” due WEDNESDAY

Unit : Covalent Bonding Ch 8 When C, O and H atoms bond in a certain way to form sugar, the resulting compound has a sweet taste. The sweetness resides neither in the C, nor in the O, nor in the H; it resides in the pattern that emerges from their interaction. -- Fritjof Capra

Molecular Shapes Molecules only have partial charges, but they still repel like charges.  What angles and shapes would let the atoms connected to a central atom be as far apart as possible? Number AtomsAngleShape

Ch 8.1 “Molecular Compounds” Objectives:  Distinguish between melting/boiling points of ionic and molecular compounds.  Describe information in a molecular formula.

Molecular Compounds  Just like these toys, atoms can also be arranged in many different ways. 8.1

Molecules and Molecular Compounds Matter can take many forms.  Noble gases, like helium and neon, are monoatomic.  Monotone means one tone. Monochrome is one color.  What does monoatomic mean? 8.1

Molecules and Molecular Compounds Molecular Bonds  Molecules are NEUTRAL groups of atoms.  Atoms share electrons aka covalent bond. 8.1

Molecules and Molecular Compounds A compound made of molecules is called a molecular compound. H 2 O and CO are molecular compounds. 8.1

Molecules and Molecular Compounds Diatomic molecule consist of two atoms.  There are 7 diatomic elements  LEARN THEM!! 8.1

Molecules and Molecular Changes Melting and boiling points  Molecular compounds tend to have relatively low melting and boiling points. 8.1

Molecules and Molecular Changes Ethane, a component of natural gas, is also a molecular compound. 8.1

Molecular Formulas  Show what elements and how many of each  Many different types of models are used. 8.1

Molecular Formulas 8.1 Different models for Ammonia # of each element Relative size of atoms Orientation in space Connections & bond type Orientation in space, bond angle & length

Molecular Formulas Formulas of some Molecular Compounds 8.1

8.1 Section Quiz. 1. Compared to ionic compounds, molecular compounds tend to have relatively  low melting points and high boiling points.  low melting points and low boiling points.  high melting points and high boiling points.  high melting points and low boiling points.

8.1 Section Quiz 2. A molecular compound usually consists of  two metal atoms and a nonmetal atom.  two nonmetal atoms and a metal atom.  two or more metal atoms.  two or more nonmetal atoms.

8.1 Section Quiz 3. A molecular formula shows  how many atoms of each element a molecule contains.  a molecule's structure.  which atoms are bonded together.  how atoms are arranged in space.

11/24 Bell Work Capt. Frank was out for a walk when it started to rain. He did not have an umbrella and he wasn’t wearing a hat. His clothes were soaked, yet not a hair on his head got wet.  How could this happen?

11/24 Schedule  Revisit “Covalent Bonding Pt. 1”  Molecular shapes in 3D  Start notes Ch 8.2 Assignments: 1.SR 8.1 “Molecular Compounds” due WEDNESDAY 2.SR 8.2 due MONDAY

Molecular Shapes Molecules only have partial charges, but they still repel like charges.  What angles and shapes would let the atoms connected to a central atom be as far apart as possible? Number AtomsAngleShape

Ch 8.2 “Nature of Covalent Bonding” Objectives  Describe how electrons are shared to form covalent bonds.  Use electron dot structures to model molecules.  Distinguish between different types of covalent bonds.

The Nature of Covalent Bonding This picture shows the hole in the ozone layer in Southern Hemisphere.  Oxygen atoms can form the oxygen (O 2 ) you breathe or ozone (O 3 ). 8.2

The Octet Rule in Covalent Bonding The Octet Rule  Electrons are usually shared so that atoms can have electron configurations like noble gases.  Write the electron configuration for Ne, F -, and Mg 2+. How many electrons does each have?

8.2 Single Covalent Bonds  Atoms that share 1 pair of electrons. Valence electrons

8.2 Single Covalent Bonds Dot Structure vs Structural Formula  Dot Structure: Shared electrons shown as dots.  Structural formula: Covalent bonds shown by lines Name these compounds.

Single Covalent Bonds  The halogens form single covalent bonds in their diatomic molecules.  Example: Fluorine. 8.2

Single Covalent Bonds  Unshared pairs of valence electron is also known as lone pairs.

Single Covalent Bonds  Hydrogen and oxygen atoms attain noble-gas configurations by sharing electrons. 8.2

Single Covalent Bonds  The ammonia molecule has one unshared pair of electrons. 8.2

Single Covalent Bonds  Methane has no lone pairs. 8.2

Section Assessment 8.1

11/25 Bell Work Two identical tanks of water are drained at the same time. One tank has one 2 cm drain and the other has two 1 cm drains. Which tank will empty faster? Explain.

11/25 Schedule  Continue notes Ch 8.2 Assignments: 1.SR 8.1 “Molecular Compounds” due TODAY 2.SR 8.2 due MONDAY

Section Assessment for Conceptual Problem 8.1

8.2 Double and Triple Covalent Bonds Other Types of Covalent Bonds  Double and triple bonds form by sharing more pairs of electrons.

8.2 Double and Triple Covalent Bonds  Double bond: 2 pairs shared  Triple bond: 3 pairs shared Double bond Triple bond

Double and Triple Covalent Bonds  Each oxygen atom has two lone pairs, a double bond gives both access to 8 electrons. 8.2

Double and Triple Covalent Bonds 8.2

Double and Triple Covalent Bonds  CO 2 is soluble in water and used to carbonate many beverages. The molecule has two carbon- oxygen double bonds.

11/30 Bell Work A group of soldiers was standing under the blistering sun facing due west. Their sergeant shouted:  Right turn!  About turn!  Left turn!  Which direction are the soldiers now facing?

11/30 Schedule  Continue notes Ch 8.2  Dot Diagram/Structure Practice Assignments: 1.SR 8.1 “Molecular Compounds” LATE 2.SR 8.2 due TODAY

8.2 Coordinate Covalent Bonds  Coordinate covalent bond: one atom contributes both bonding electrons.  In a structural formula, show coordinate covalent bonds as arrows that point from the atom donating the pair of electrons to the atom receiving them.

Coordinate Covalent Bonds In carbon monoxide, oxygen has a stable configuration but the carbon does not. 8.2

Coordinate Covalent Bonds The problem is solved if the oxygen donates one of its unshared pairs of electrons for bonding.

Coordinate Covalent Bonds A polyatomic ion, is a tightly bound group of atoms that has a positive or negative charge and behaves as a unit. 8.2 Ammonium (NH 4 + ) is commonly found in fertilizers.

Coordinate Covalent Bonds 8.2

Section Assessment 8.2

Section Assessment 8.2

Section Assessment for Conceptual Problem 8.2

Bond Dissociation Energies  Bond Dissociation Energy: Energy required to break a covalent bond.  High dissociation energy = strong covalent bond 8.2 Single bonds easier to break than double or triple.

Demo: Bond Energies  Watch as the Mg ribbon and sugar are ignited.  Both reactions form oxides. Which one is covalent? Ionic? 2Mg + O2  2MgO + energy C 12 H 22 O O 2  12CO H 2 O

Resonance Resonance: Dot structures do not completely describe lab results  Actual molecule is a hybrid of the dot structures. 8.2

Resonance A resonance structure is a structure that occurs when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion. 8.2

Resonance Ozone in the upper atmosphere blocks harmful UV radiation. At lower elevations, it contributes to smog. 8.2

Exceptions to the Octet Rule  Molecules with an odd number of total valence electrons.  There are also molecules in which an atom has fewer, or more, than 8.  Boron (6)  Sulfur (10 or 12)  Phosphorus (10) 8.2

Exceptions to the Octet Rule Two electron dot structures can be drawn for the NO 2 molecule. 8.2

Exceptions to the Octet Rule NO 2 is produced naturally by lightning strikes. 8.2

Exceptions to the Octet Rule The electron dot structure for PCl 5 can be written so that phosphorus has ten valence electrons. 8.2

8.2 Section Quiz. 1. In covalent bonding, atoms attain the configuration of noble gases by  losing electrons.  gaining electrons.  transferring electrons.  sharing electrons.

8.2 Section Quiz 2. Electron dot diagrams are superior to molecular formulas in that they  show which electrons are shared.  indicate the number of each kind of atom in the molecule.  show the arrangement of atoms in the molecule.  are easier to write or draw.

8.2 Section Quiz 3. Which of the following molecules would contain a bond formed when atoms share three pairs of electrons?  Se 2  As 2  Br 2  Te 2

Element Mask Analogy – DUE MONDAY 1.Draw a theatre mask that covers most of a sheet of copy paper. Fold it in half. 2.On one side, write and illustrate 5 things that describe your personality. 3.On the other, describe and illustrate the element that is most like you. Explain. Personality Element & explanation