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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
slide3

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-
slide5

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
slide10
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…
  • 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
  • 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- a covalent molecule
  • Polarity of water makes it the universal solvent.. Able to dissolve many substances..
  • Not all!!
non polar molecules
Non Polar Molecules
  • Even distribution of charge
  • Examples: oxygen gas O2
cov vs ionic bonds electronegativity counts
Cov 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
  • 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
  • http://www.ptable.com
your turn
Your Turn
  • 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
  • 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?
slide21
BLACK Intra Forces-within molecule-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
  • 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
slide23

Diamond and graphite examples of Carbon in covalent bonding

  • 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
molecular compounds nomenclature
Molecular Compounds Nomenclature
  • 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
slide27

Communicate first element

  • 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
  • N2O5
  • Carbon dioxide.. To write this formula properly, what is dropped?
  • Sulfur trioxide
  • SF6
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