chapter 8
DESCRIPTION
Chapter 8. Bonding. Lewis Structures. Diagram that shows American chemist Gilbert N. Lewis Dots = Paired dots = Simple way of showing electrons Most reactions involve only. Lewis Structures. When drawing: Use electron configuration Move in clockwise direction… “12” = s orbital - PowerPoint PPT PresentationTRANSCRIPT
Chapter 8Chapter 8
BondingBonding
Lewis StructuresLewis Structures
Diagram that shows Diagram that shows American chemist Gilbert N. LewisAmerican chemist Gilbert N. Lewis Dots = Dots =
Paired dots = Paired dots = Simple way of showing electronsSimple way of showing electrons Most reactions involve only Most reactions involve only
Lewis StructuresLewis Structures
When drawing:When drawing: Use electron configurationUse electron configuration Move in clockwise direction…Move in clockwise direction… ““12” = s orbital12” = s orbital ““3, 6, 9” = p orbitals – fill each with ONE 3, 6, 9” = p orbitals – fill each with ONE
electron before filling with pairs…electron before filling with pairs… Just like orbital filling diagram…Just like orbital filling diagram…
Examples: draw Lewis Structures of B, N, Examples: draw Lewis Structures of B, N, F, NeF, Ne
The Ionic BondThe Ionic Bond Ionic bond: Ionic bond:
Transfer of electrons from Transfer of electrons from Ions form with Ions form with Attraction between electrostatic charges Attraction between electrostatic charges
is a strong forceis a strong force which holds which holds
atoms atoms togethertogether
The Ionic BondThe Ionic Bond NOT A NOT A
Bond not just Bond not just between (for between (for example) one example) one sodium and one sodium and one chloridechloride
The Ionic BondThe Ionic Bond
Typically Typically Metals usually Metals usually Nonmetals usually Nonmetals usually
Predicting Formulas of Ionic Predicting Formulas of Ionic CompoundsCompounds
In almost all stable chemical In almost all stable chemical compounds of representative compounds of representative elements, each atom attains a elements, each atom attains a
This concept forms the basis for our This concept forms the basis for our understanding of chemical bonding.understanding of chemical bonding.
Predicting Formulas of Ionic Predicting Formulas of Ionic CompoundsCompounds
How many electrons must be gained How many electrons must be gained or lost to achieve noble gas or lost to achieve noble gas configuration?configuration? Ba must lose Ba must lose
Forms the ion Forms the ion S must gain S must gain
Forms the ion Forms the ion So…must be ratio of So…must be ratio of
Predicting Formulas of Ionic Predicting Formulas of Ionic CompoundsCompounds
Elements in a family usually form Elements in a family usually form compounds with the same atomic compounds with the same atomic ratiosratios Because they have the same number of Because they have the same number of
valence electronsvalence electrons Must gain or lose the same number of Must gain or lose the same number of
electronselectrons See table 11.4 pg 233See table 11.4 pg 233
Predicting Formulas of Ionic Predicting Formulas of Ionic CompoundsCompounds
The formula for sodium oxide is The formula for sodium oxide is NaNa22O. Predict the formula for O. Predict the formula for Sodium sulfide Sodium sulfide
Predicting Formulas of Ionic Predicting Formulas of Ionic CompoundsCompounds
Rubidium OxideRubidium Oxide Rubidium Rubidium Oxygen Oxygen So…formula must be So…formula must be This makes sense b/c rubidium is in This makes sense b/c rubidium is in
same family as sodiumsame family as sodium
The Covalent BondThe Covalent Bond A pair of A pair of Most common type of bondMost common type of bond Stronger than Stronger than Electron orbital expands to include both Electron orbital expands to include both
nucleinuclei most often foundmost often found between between
Negative chargesNegative charges
allow positive nucleiallow positive nuclei to be drawn close to be drawn close
to each other to each other
The Covalent BondThe Covalent Bond
Atoms may share more than one pair of Atoms may share more than one pair of electronselectrons Double bond – Double bond – Triple bond – Triple bond – Multiple bonds are Multiple bonds are
Covalent bonding between identical atoms Covalent bonding between identical atoms
means electrons are shared means electrons are shared Covalent bonding between different atoms Covalent bonding between different atoms
leads to leads to
ElectronegativityElectronegativity
The attractive force that an atom of The attractive force that an atom of an element has for an element has for
Atoms have different Atoms have different electronegativitieselectronegativities Electrons will spend more time near Electrons will spend more time near
atom with atom with So…one atom assumes a partial So…one atom assumes a partial The other assumes a partial The other assumes a partial
ElectronegativityElectronegativity
Electronegativity trends and periodic Electronegativity trends and periodic tabletable See table 11.5 page 237See table 11.5 page 237 Generally increases from Generally increases from Decreases Decreases Highest is Highest is Lowest is Lowest is
ElectronegativityElectronegativity Polarity is determined by Polarity is determined by
difference in electronegativitydifference in electronegativity Nonpolar covalentNonpolar covalent
Polar covalentPolar covalent
Ionic compoundIonic compound
ElectronegativityElectronegativity
If the electronegativity difference is If the electronegativity difference is greater thangreater than
Above Above Below Below
ElectronegativityElectronegativity
Polar bonds form between two atomsPolar bonds form between two atoms Molecules can also be polar or nonpolarMolecules can also be polar or nonpolar
DipoleDipole
PolarPolar
NonpolarNonpolar
Lewis Structures of Lewis Structures of CompoundsCompounds
Convenient way of showing ionic or Convenient way of showing ionic or covalent bondscovalent bonds
Usually the single atom in a formula Usually the single atom in a formula is the central atomis the central atom
The Ionic BondThe Ionic Bond LEWIS STRUCTURES of ionic bondsLEWIS STRUCTURES of ionic bonds
The Covalent BondThe Covalent Bond LEWIS STRUCTURES of covalent LEWIS STRUCTURES of covalent
bondsbonds Use dashes instead of dots…Use dashes instead of dots…
The Covalent BondThe Covalent Bond
Lewis Structures of Lewis Structures of CompoundsCompounds
1)1) Obtain the total number of valence Obtain the total number of valence electronselectrons
1)1) Add the valance electrons of all atomsAdd the valance electrons of all atoms
2)2) Ionic – add one electron for each Ionic – add one electron for each negative charge and subtract one negative charge and subtract one electron for each positive chargeelectron for each positive charge
Lewis Structures of Lewis Structures of CompoundsCompounds
2)2) Write the skeletal arrangement of Write the skeletal arrangement of the atoms and connect with a single the atoms and connect with a single covalent vondcovalent vond
3)3) Subtract two electrons for each Subtract two electrons for each single bond single bond
1)1) This gives you the net number of This gives you the net number of electrons available for completing the electrons available for completing the structurestructure
Lewis Structures of Lewis Structures of CompoundsCompounds
4)4) Distribute pairs of electrons around Distribute pairs of electrons around each atom to give each atom a each atom to give each atom a noble gas structurenoble gas structure
5)5) If there are not enough electrons If there are not enough electrons then try to form double and triple then try to form double and triple bonds bonds
Lewis Structures of Lewis Structures of Compounds Compounds
Write the Lewis Structure for Write the Lewis Structure for methane CHmethane CH44
Lewis Structures of Lewis Structures of CompoundsCompounds
Carbon Dioxide, COCarbon Dioxide, CO22
Complex Lewis StructuresComplex Lewis Structures
Some molecules and polyatomic ions Some molecules and polyatomic ions have strange behaviors…have strange behaviors… No single Lewis structure is consistentNo single Lewis structure is consistent If multiple structures are possible the If multiple structures are possible the
molecule showsmolecule shows
Complex Lewis StructuresComplex Lewis Structures
Carbonate ion, COCarbonate ion, CO332-2-
Compounds ContainingCompounds ContainingPolyatomic IonsPolyatomic Ions
Polyatomic ion: Polyatomic ion:
Behaves as a single unit in many Behaves as a single unit in many chemical reactionschemical reactions
Sodium carbonate (NaSodium carbonate (Na22COCO33))