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Covalent Bonds. http://www.ptable.com. Octet Rule must be satisfied-reach noble gas state What of elements that meet and cannot completely transfer e- and satisfy octet rule for each? H and H atom story…one happy if e- tranfer other sad. Both atoms get one e-

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Http www ptable com
http://www.ptable.com

  • Octet Rule must be satisfied-reach noble gas state

  • What of elements that meet and cannot completely transfer e- and satisfy octet rule for each?

  • H and H atom story…one happy if e- tranfer other sad


  • Both atoms get one e-

  • Both satisfy octet rule by SHARING

  • Each atom must have both e-

  • DIRECTIONAL bond- product of shared e-

  • Each H atom will have full outer energy level


Hydrogen gas h 2
Hydrogen gas H2

  • Two H atoms sharing each other’s e-


  • Oxygen gas shares 4 valence e- or

    2 pairs valence e-

  • Results in a double bond

  • Nitrogen gas shares 3 pairs of valence e-

  • Results in triple bond

  • Hydrogen, fluorine, nitrogen, chlorine…

  • BrINClOF (Chlorine is capital C lower case l)


Remember how to do this 1s2
Remember how to do this?1s2…

  • Each bond represents 2 shared e-


Nature of covalent bonds
Nature of Covalent Bonds

  • Strong electrostatic attraction between shared valence e- and + nucleus

  • One end of molecule has more + than

    – charge


Draw lewis dots and show how water molecule shares e
Draw Lewis dots and show how water molecule shares e-

  • Covalent bond VERY STRONG

  • Shared e- confined so bond is

    DIRECTIONAL


Covalent vs ionic bonds
Covalent vs. Ionic Bonds

  • http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/bom1s2_11.swf


http://www.bing.com/videos/search?q=ionic+vs+covalent+bonding&FORM=VIRE3&adlt=strict#view=detail&mid=D0981F9E5http://www.bing.com/videos/search?q=ionic+vs+covalent+bonding&FORM=VIRE3&adlt=strict#view=detail&mid=D0981F9E5

  • video


H tends to share only e octet rule not satisfied by giving up e
H tends to share only e- Octet rule not satisfied by giving up e-

  • H and Cl… HCl

  • Chlorine tends to grab at e-

  • Doesn’t want to give it up…

  • Uneven distribution of e- density

  • ELECTRONEGATIVITY becomes important

    ᵟsmall delta indicates charge – or + ᵟ+ H Cl ᵟ-


Result is
Result is… up e-

  • POLARITY

  • A partial charge separation

  • Electronegativity increases e- moves towards the area

  • In covalent bonds, neither atom has energy to remove e- from other atom


Example of a polar covalent molecule
Example of a polar covalent molecule up e-

  • H-O-H Water H2O

  • Stable octet for oxygen.. Completed with other H atom


Notice how directional the bonds are for water a covalent molecule
Notice how directional the bonds are for water- up e-a covalent molecule

  • Polarity of water makes it the universal solvent.. Able to dissolve many substances..

  • Not all!!


Non polar molecules
Non Polar Molecules up e-

  • Even distribution of charge

  • Examples: oxygen gas O2


Cov vs ionic bonds electronegativity counts
Cov up e- vs. Ionic Bonds Electronegativity counts

  • Hydrogen Gas molecule: H2

    No difference of attraction of electrons between 2 atoms so ΔEN=O

    (Capital Delta Δ means change)

    Hydrogen gas is a non polar covalent molecule

    Water is polar covalent


En and bond types
EN and bond types up e-

  • 0 = non polar cov

  • < 0.3 no polar cov

  • 0.3- 0.4 slightly polar cov

  • 1.0-1.7 polar cov

  • More and more separation of charges

  • If difference > 1.7 then generally ionic!


Go to ptable com
Go to ptable.com up e-

  • http://www.ptable.com


Your turn
Your Turn up e-

  • Use EN # on PT to determine difference in EN between elements of a compound and type of bond formed between them.

    NaBr

    Water

    CS2


Inter and intra prefixes
Inter and Intra prefixes up e-

  • Forces may be intra or intermolecular in nature.

  • H:H molecule of hydrogen gas

  • Can 3rd H come into the molecule?

  • No Pauli Exclusion Principle

  • Molecules formed with hydrogen gas.

  • Bond very strong .. What’s in between molecules?


BLACK Intra Forces-within molecule- up e-RED Inter Forces- between or among molecules as they exist in natural state

Intermolecular forces weaker than intramolecular forces

The unit formed is called a molecule


Properties of covalent diatomic elements and compounds
Properties of Covalent (diatomic) Elements and Compounds up e-

  • Dull no free e-

  • Soft, brittle- weak intermolecular forces

  • Low mp and bp- weak intermolecular forces

  • NO conductivity as solid or molten (no charges)

  • Some soluble in water Aqueous solutions DO NOT conduct electricity at all- no free moving charged particles


  • Diamond and graphite examples of Carbon in covalent bonding up e-

  • Microstructures in diamond very different from graphite

  • Both covalent, both made of carbon only

  • Diamond- strong interactions of directionality of carbon atoms- lattice like STRONG BONDS

  • Graphite- weaker bonds due to direction and spaces between atoms allows for breakage- leaving of powder from pencil


Diamond
diamond up e-


Graphite
graphite up e-


Molecular compounds nomenclature
Molecular Compounds Nomenclature up e-

  • State how many of each element in compound

  • Water H-O-H

  • FIRST: must know prefixes:

  • 1. Mono

  • Di

  • Tri

  • Tetra

  • Penta

  • Hexa

  • Hepta

  • Octa

  • Nona

  • Deca


  • Communicate first element up e-

  • Assume same name as element’s name

  • 2nd element “ide” notation

  • ONE exception: if 1 is coefficient for 1st element then it is dropped

  • WATER? Dihydrogen monoxide


Your turn1
Your Turn up e-

  • N2O5

  • Carbon dioxide.. To write this formula properly, what is dropped?

  • Sulfur trioxide

  • SF6


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