Chemistry - Covalent Bonding
Upcoming SlideShare
Loading in...5
×
 

Chemistry - Covalent Bonding

on

  • 3,583 views

 

Statistics

Views

Total Views
3,583
Views on SlideShare
3,577
Embed Views
6

Actions

Likes
9
Downloads
197
Comments
0

2 Embeds 6

http://chemistryfreaks.com 3
http://www.chemistryfreaks.com 3

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Chemistry - Covalent Bonding Chemistry - Covalent Bonding Presentation Transcript

    • Covalent Bonding
    • Sections 8.1, 8.2, 9.3, and *8.4* Sections 6.1 16.1, 6.5 and *16.3*
    • Remember…
      • Ionic bonds form between…
      • An ionic bond happens when one atom… and the other atom…
    • Remember…
      • The definition of ionic bond is…
      • The chemical formula of an ionic compound represents a…
      • The four sentences above represent four of the most essential differences between molecular and ionic compounds.
      • These differences are so important that…
    • Essay Question: Test 3-1
      • Define ionic bond and covalent bond. Outline and define, in detail, four major differences between ionic compounds and molecular (covalent) compounds.
    • Molecular Compounds
      • Formed by covalent bonds
      • Ionic compounds are generally crystalline solids at room temperature.
      • Molecular compounds (CO 2 and water, for example, have VERY different properties.)
    • Molecular Compounds
      • Molecular compounds are formed through covalent bonds.
      • Covalent bonds are created when atoms SHARE electrons, instead of gaining and losing them.
    • Vocabulary
      • Molecule : group of atoms joined by covalent bonds
      • Diatomic molecules : molecules consisting of two atoms
      • Molecular formula : shows how many atoms of each element a molecule contains
    • Think About It…
      • Chlorine is a diatomic element, meaning that it exists in its atomic state as two bonded atoms.
      • Draw two chlorine atoms.
      • Is the bond between these two atoms ionic or covalent? How do you know?
    • Properties of Molecular Compounds
      • Covalent bonds usually occur between…
      • Often are gases or liquids at room temperature
      • Images will show atoms “stuck” to one another
    • Properties of Molecular Compounds
      • In general, melting and boiling points of molecular compounds are lower than ionic compounds
    • Molecular Formulas
      • Molecular formula of a molecular compound shows how many atoms of each element are in ONE MOLECULE of the compound.
      • (Contrast this with the chemical formula of ionic compounds, which show only the ratio of elements in the compound.)
    • Molecular Formulas
      • Example:
      • IONIC: Calcium chloride – CaCl 2
        • Means that in the compound there are two chloride ions for every one calcium ion
      • COVALENT: Carbon dioxide – CO 2
        • Means that each carbon dioxide molecule consists of one carbon atom bonded to two oxygen atoms
    • Molecular Compounds
      • Molecular compounds can be significantly larger than ionic compounds.
      • Benzoic Acid: C 7 H 6 O 2
      • 2,4-Dichlorophenoxyacetic acid: C 8 H 6 Cl 2 O 3
    • Molecular Compounds
      • Formulas not always in lowest terms
      • Example: Ethane C 2 H 6
      • Formulas do not give molecule’s structure. (It must be inferred.)
    • Structure Diagrams
      • Molecular Formula
      • Structural Formula
      • Ball-and-stick model
      • Space Filling Model
      • Perspective drawing
    • Forming Covalent Bonds
    • Octet Rule
      • In covalent bonds, atoms share electrons so that they fill their valence levels
      • Usually 8 (but only 2 for hydrogen)
    • Single Covalent Bonds
      • Atoms held together by sharing one pair of electrons are said to form a SINGLE COVALENT BOND
      • Each atom donates one electron to the bond
    • Single Covalent Bonds Cl Cl Cl Cl
    • Single Covalent Bonds Cl Cl Cl Cl
    • Single Covalent Bonds Cl Cl Cl Cl Single Bond Lone Pairs
    • Covalent Bonds
      • Electrons that do not take part in the bond are called “lone pairs” or “unshared pairs”
    • Covalent Bonds
      • Different elements can form different numbers of bonds
      • Group 7A elements need one more electron, and can form one bond
      • Group 6A elements need two more electrons and can form two bonds
      • Group 5A – three bonds
      • Group 4A – four bonds
      There are exceptions! Hydrogen, too!
    • Working With Covalent Bonds
      • Draw the electron dot structures.
      • Determine arrangement.
      • Replace shared pairs of electrons with a line. (Leave lone pairs.)
    • Draw Structural Formulas
      • NH 3
      • H 2 S
      • PBr 3
    • Draw Structural Formulas
      • H 2 O
      • CH 4
      • OF 2
    • Draw Structural Formulas
      • SCl 2
      • N 2 H 4
      • CCl 4
      • CHCl 3
      • C 2 H 6
      • HF
      Usually, the atom that can form MORE bonds will be in the center of the molecule!
    • Draw Structural Formulas, Part 2
      • OBr 2
      • P 2 H 4
      • CI 4
      • CH 2 Br 2
      • C 2 Cl 6
      • HCl
      • C 3 H 8
      Usually, the atom that can form MORE bonds will be in the center of the molecule!
    • Double and Triple Bonds
    • Double Covalent Bonds
      • Atoms attain noble gas configuration by sharing two pairs of electrons (four)
      • Bond length is shorter
    • Double Covalent Bonds
      • Oxygen has 6 valence electrons
      • O (Group 6A) can form two bonds
      O O
    • Double Covalent Bonds
      • Oxygen has 6 valence electrons
      • O (Group 6A) can form two bonds
      O O
    • Double Covalent Bonds
      • OCTET RULE NOT FULFILLED!
      O O
    • Double Covalent Bonds
      • OCTET RULE NOT FULFILLED!
      O O
    • Double Covalent Bonds
      • OCTET RULE FULFILLED!
      O O
    • Other molecules with double covalent bonds are…
      • CO 2
      • Ethene, C 2 H 4
      • Carbonyl, COH 2
    • Double Covalent Bonds
      • When counting number of valence electrons, double bonds count as 4 shared electrons.
      • Hydrogen will not form double covalent bonds… why?
    • Triple Covalent Bonds
      • Atoms attain noble gas configuration by sharing three pairs of electrons (six)
      • Bond length is even shorter
    • Triple Covalent Bonds
      • Nitrogen has 5 valence electrons
      • N (Group 5A) can form three bonds
      N N
    • Triple Covalent Bonds
      • Nitrogen has 5 valence electrons
      • N (Group 5A) can form three bonds
      N N
    • Triple Covalent Bonds
      • OCTET RULE NOT FULFILLED!
      N N
    • Triple Covalent Bonds
      • OCTET RULE NOT FULFILLED!
      N N
    • Triple Covalent Bonds
      • OCTET RULE NOT FULFILLED!
      N N
    • Triple Covalent Bonds
      • OCTET RULE NOT FULFILLED!
      N N
    • Triple Covalent Bonds
      • OCTET RULE FULFILLED!
      N N
    • Other molecules with triple covalent bonds are…
      • Acetylene, C 2 H 2
      • Hydrogen Cyanide, HCN
      • Propyne, C 3 H 4
    • Triple Covalent Bonds
      • When counting number of valence electrons, triple bonds count as 6 shared electrons.
    • Diatomic Elements
    • Diatomic Elements
      • Diatomic elements exist in their atomic forms as binary molecular compounds, since covalent bonds form between the atoms
      • i.e. a “molecule” of oxygen gas is O 2 , not O
    • Diatomic Elements
      • F 2
      • Cl 2
      • Br 2
      • I 2
      • H 2
      • N 2
      • O 2
    • Exceptions To The Octet Rule
    • Exceptions
      • Compounds cannot satisfy the Octet Rule for all atoms if the total number of valence electrons is odd.
      • NO 2 – total number of valence electrons is 17
      O O N
    • More Exceptions…
      • Nonmetals in the third period and beyond can form more than 4 bonds, since they have empty d orbitals where they can “promote” or “store” extra s or p electrons.
      • Ex.: Phosphorus can form 5 bonds.
    • Naming Binary Molecular Compounds
    • Naming Molecular Compounds
      • CO and CO 2 are very different compounds
      • How can we distinguish them in their names?
    • Naming Molecular Compounds
      • Confirm that the compound is molecular, not ionic.
      • Name the elements in the order listed in the formula.
      • Add prefixes to identify the numbers of each atom in the compound.
    • Prefixes Used Mono- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5 Hexa- 6 Hepta- 7 Octa- 8 Nona- 9 Deca- 10
    • Naming Molecular Compounds
      • Omit the prefix “mono-” on the first element in the name.
      • Add “-ide” as a suffix at the end of the second element’s name.
    • Examples
      • N 2 O
      • Nitrogen oxygen
      • Dinitrogen monoxygen
      • DINITROGEN MONOXIDE
    • Practice: Write the Molecular Formula
      • Nitrogen trichloride
      • Carbon tetrabromide
      • Diphosphorus trisulfide
    • Practice: Write the Name
      • Cl 2 O 8
      • PH 3
      • N 2 O 4
      • SF 6
      • H 2 O
      • S 2 F 10
      • PCl 5
      • N 2 F 6
    • Polar Bonds and Molecules
    • Electronegativity
      • A measure of how well an atom attracts electrons
      • Measured in “Paulings”
      • In a molecule, some atoms more forcefully attract electrons than others
    • Electronegativity
      • Decreases from top to bottom
      • Increases from left to right
    • Polar Bonds
      • Polar bond – covalent bond in which electrons are shared UNEQUALLY
      • Difference in electronegativity values controls whether bond is nonpolar, polar, or ionic
    • Polar Bonds
      • Differences:
      • 0.0-0.4  nonpolar covalent
      • 0.4-2.0  polar covalent
      • 2.0+  ionic
    •  
    • Polar Bonds
      • Greek letter Delta (δ) represents the partial charge acquired by atoms in a polar bond
      • H 2 O
      • HF
      • CO 2
    • Intermolecular Attractions
      • Polar molecules attracted to one another (called dipole interactions)
      • Hydrogen bonds are attractions that occur between hydrogen and unshared electrons on another molecule
    • Test Review
    • Test Review
      • Covalent bonds – definitions
      • Molecular vs. ionic compounds
      • Writing structural formulas
      • Writing molecular formulas (from name or from structure)
      • Writing compound names
      • Information on Polar Bonds (pg. 237-240)