Ch 6 Covalent Bonds.pdf

Just a little extra information!

• Vsauce 5 min on size of internet!!! 50 grams?

Molecular Compounds

• Substances that are covalently bonded are called Molecular compounds

• Shared electrons

Nitrogen triiodide detonation

• http://www.youtube.com/watch?v=2KlAf936E 90

Bond Length and strength

• The stronger the bond, the more energy it takes to break the bond.

Bonds make atoms Stable

• Shorter are more stable….and take more energy to break!

• Bonds work a lot like springs!

Electronegativity Chart(p 194)

• Finding the difference in electronegativity helps you decide what type of bonding

Differences in Electronegativities

Like p. 195 on its side.

Types of Bonds

• If the electronegativity differences are < .4 the bonds are nonpolar covalent

• Between and including .4 and 2.1, they are polar covalent

Polar vs Nonpolar bonds: look at

Electronegativity differences

Polar molecules

Polar molecules

• Polar molecules = are molecules with partial

Polar vs Nonpolar Molecules

Nonpolar Covalent Bonds

• HONClBrIF These are always Nonpolar Cov.

Intermolecular Forces

• Resulting attraction from forces between molecules: example:London forces are between nonpolar substances

• hydrogen bonds are “strong” intermolecular forces(weaker than chemical bonds) ex: DNA, water.

Do Section Reviews p. 197 1-6

• 1. Describe the attractive and repulsive forces that occur as two atoms are brought closer together.

• 2. What happens to the stability and energy of two atoms as they form a covalent bond?

• _{3. List three differences between molecular and ionic}

compounds…

• 4. Classify each bond Cs—Br H—S Ca—O Si—Cl

• 5. Compare electrons in nonpolar and polar cov.bonds

• 6. H—C bonds???

Kahn Academy

Sec 6-2 Lewis Structures

• Valence electrons are shown on dot diagrams or “Lewis Structures” named for Gilbert N.

Unshared Pairs or Lone Pairs

How to draw Lewis Structures(p. 199)

• 1. Determine the total number of valence electrons in the compound.Ex. HCl 1+7=8

• 2. Arrange the atom’s symbols to show how they are bonded and show valence electrons as dots.

Hydrogens go on outside.Lowest

electronegativity in center. So do Halogens!

• 3. Compare the number of valence electrons

Lewis Structures cont.

• 4. Change shared electrons to a single dash.

• 5. Check to make sure all atoms(except H) follow

the octet rule.

Try some on a WHITE Board!

• Let’s make a Lewis Structure for Bromine. (Br₂)

• Next H₂

• CH₄

• H₂O

More Dot Diagrams

• NH₃

Polyatomic ions

Double Bonds + Triple Bonds

• Atoms can share more than one set of electrons in a molecule.

• Double bond = when 2 pairs of electrons are

Triple bonds

• Triple bond = When 2 atoms share 3 pairs of

Draw a Lewis Structure for

Ethane,ethene and ethyne

• C₂H₆

• C₂H₄

Ethyne(acetylene gas)

• Carbide lamps use calcium carbide and water to make gas…

Resonant hybrids (show flippy ball)

Resonance hybrid =

When more then

one Lewis structure is correct.

Try one…Carbonate Ion

Lewis Structures for Acids

• Bond the Hydrogen to an Oxygen

• 3 min youtube of Acids

• Example HNO₃

From Pink worksheet…YIKES!

Yet another version of Lewis Structure

lesson…

QUIZ!!! On lewis Structures

• Try some easy ones…. F H O C

• Next how about Cl₂ Br₂

• Now single bonds: H Br H₂O

• REMEMBER the LOWEST electronegativity goes in the central atom.

• Satisfy the Octet rule. Except for H

Naming molecular compounds

• Using Roots, prefixes and suffixes

• Mono=1, di=2, tri=3, tetra=4,penta=5, hexa=6, hepta=7, octa=8, nona=9, deca=10 (see wall)

• OMIT mono in first element’s names:ex:

Carbon monoxide NOT monocarbon monoxide

Naming Molecular Compounds

• There are two Systems for naming molecular compounds.

– 1. Prefix/Root/Suffix ( Ex: Iron trichloride)

– 2. Ionic Compounds(Stock Method with Roman Numerals or oxidation numbers)

Sample Problems

• P₂O₃ =

– Diphosphorus trioxide

• P₂O₅

– Diphosphorus pentoxide

• CCl₄

– Carbon Tetrachloride

• SO₂

FYI

Never trust an Atom….

Stock Method…naming

• The second way is to use oxidation numbers to name the compound.

• Oxygen always has an oxidation number of -2

Sec 6-2 Concept/Reviews

• 7. Draw two resonance hybrids for SO2

• 8. Draw Lewis structures for ClO₃- _{and SO} 4

2-• 9. Draw two fo the resonance structures for CO₃2-

• 10. Write the number of valence electrons for

atoms with the following electron configurations

A. 1s2_2s2 _{b. 1s}2_2s2_2p6_3s2_3p4 _{c. 1s}2_2s2_2p6_3s2_3p5

11. Draw Lewis Structures Br2 b. (Ozone) O₃ c. SO₃ d. H₃0+ 12. Name using prefixes…a. SiO₂ b. SO₂ c. CF₄ d. N₂O₃

13. Give oxidation numbers a. PBr₅ b. PBr₃ c. H₂SO₄ d. SO₃ e. CCl₄

6-3 Empirical Formulas

• Determined experimentally

• Like last chapter…if you have percentages assume 100 g and go from there.

• If you know molecular formula’s mass…just divide by emp formula’s mass to get x

Empirical Formula

• Empirical Formula = Formula showing the

smallest whole number ratio of atoms.

– Empirical Formula of glucose = CH₂O

Molecular Formula

• Molecular formula = formula showing the

actual number of atoms in a molecule.

Structural Formula

• Structural formula = formula showing how

6-4 Shapes of Molecules this is due to

VSEPR-Valence Shell Electron Pair

Repulsion

• 1st Draw the Lewis Structure for the molecule

• 2nd _{Count the number of electron CLOUDS}

surrounding the central atom: Each bond counts as a cloud and each nonbonded pair count as a cloud

• 3rd _{Use: Two electron clouds= LINEAR}

Examples of Shapes

• Linear(two bonds)

• 180 degrees

• Trigonal Planar(3 bonds)

Tetrahedral

Pyramidal

Bent

Additional shapes

Internet Lewis Structures quiz

STOP!!!!Let’s do test on sec 6-1…6-4

6-5 Carbon Bonding(organic chem)

• Carbon has Four bonds…so lots of possibilities!

• Whole classes/books designated to Carbon Chemistry.

• KNOW FOR QUIZ ON __________(see wall) And yes, it will be covered up!

Hydrocarbons: Methane, Ethane, Propane,

Butane, Pentane, Hexane, Heptane, Octane…

Organic compounds

• Organic compounds come in many different shapes.

• Chains and Rings

Hydrocarbons

• Hmmmmm, What can they be made of?

Hydrocarbons are molecules formed of hydrogen and carbon

Polymers /Nylon/slime

• Steve Spangler 3 min movie

Organic Functional Groups

• Alcohol end in –ol

• Ether

• Aldehyde

Esters( the smelly Organic Functional

Group!)

• Esters are made from acids and alcohols.

More Organic Functional Groups(see

wall)

• Ketone

Meth…err methamphetamine

Examples

• 1st _{Find the Parent chain ( or cycle)}

• 2nd Number so that smallest sum is possible

Organic structure models

• Every bend and end is a Carbon atom…