bonding. video 5.1 types of bonds octet rule review atoms bond with other atoms by sharing or...
TRANSCRIPT
Bonding
Video 5.1Types of Bonds
Octet Rule Review
Atoms bond with other atoms by sharing or transferring electrons in order to achieve a stable octet (8 valence electrons). Bonding creates stability!
*When bonds are formed energy is ___________.
*When bonds are broken energy is ___________.
released
absorbed
Ionic BondsO Transfer of
electrons from the cation to the anion (metal to nonmetal).
O High melting point and boiling point
O Mostly hard crystalline solids
O Conduct as liquid (either melted or dissolved) due to mobile ions.
Ionic BondsSodium Chloride: NaCl (table salt) properties:O HardO Solid crystalsO High melting point,
forget boiling!O Liquid phase
conducts (electrolytes are salts)
Metallic BondsO Metals onlyO All metals lose their
valence electrons and form a sea of electrons
O High melting point and boiling point
O Insoluble in waterO Always able to conduct
heat and electric due to mobile electrons
O MalleableO Ductile
Metallic Bonds
Copper (Cu) properties:O Hard solidO High melting
point, forget boiling!
O Malleable and ductile
O ConductorO Can’t dissolve
Metallic BondsSea of electrons
Copper (I) ions Copper (II) ions
Covalent Bonds (Molecular)O Nonmetals onlyO Share electrons
between atomsO Low melting
point and boiling point
O Never conduct heat or electricity
O Soft solid or gas
Covalent Bonds
Dextrose C6H12O6
(Sugar) properties:O SoftO Melts easily in
sauce pans for caramel
O Doesn’t conduct (nonelectrolyte)
What type of bond is created?
1. Ca + O2. K + Br3. S + Cl4. I + S5. Li + Mg6. Ba + S
M+ NM = Ionic
NM + NM = Covalent
M + NM = Ionic
M + NM = Ionic
NM + NM = CovalentM + M = Metallic
Video 5.2Ionic Compounds
Review: Find the ionic formula:
1. K + Br
2. Mg + Cl
3. Na + S
4. Ca + S
KBr
MgCl2
Na2S
CaS
+ -
+2
-
+ -2
+2
-2
Draw Lewis structures:KBr
MgCl2
Na2S
CaS
Which subatomic particle is involved in bonding?
Electrons only!
Geometry of ionic crystals
Ions
Ionic crystal
Video 5.3Covalent Compounds
Covalent Lewis Structures Rules: CCl4
1. Add up all valence e-
2. Draw a skeletal structure with bonds between elements. Least frequent element in the middle.
3. Subtract 2e- from total for each bond drawn.
4. Draw in remaining e- to fill each atom’s octet.
5. Evaluate: each atom should have 8 e- only.
C: 4 + 4Cl: 7 = 32 valence e-
ClCl—C—Cl Cl
32-8=24
VSEPR
“Valence shell electron pair repulsion” is a model for molecules. Lone electron pairs are repelled by one another and should be placed as far apart as
possible.
Geometry1. Linear: The molecule is on one plane
(flat) such as CO2 or H2.
2. Bent: The molecule is bent at angle like H2O due to unshared electrons and two bonding pairs on the central atom.
Geometry3. Pyramidal: The molecule has a triangular
shape like NH3 due to a lone pair and three bonding pairs on the central atom.
4. Tetrahedral: The molecule has four bonding pairs and no lone pairs on
the central atom like CH4.
Examples:O Draw the following molecules and identify
their geometry:
1. PCl32. SiCl2H2
3. Br2
4. H2S
pyramidal
tetrahedrallinear
bent
Video 5.4Bond Polarity
Bond PolarityThe earth has two poles; North and South.
A magnet also has two poles.
Bonds may have two poles. This means one element is charged different than the other.
If a bond is polar, the two elements have different electronegativities. The element with a higher electronegativity will be more negative.
Bond Polarity
Bond Polarity
Nonpolar Bond
Bond PolarityElectronegativity
differenceBond type
0-0.4 Nonpolar
0.5-1.0 Polar
1.1-2.0 Very Polar
2.0-4.0 Ionic
Ionic, polar or nonpolar?1. C-Br2. Na-S3. C-C4. H-O5. K-O6. Be-B
7. As-O8. N-O9. C-O10.F-F11.S-C12.N-H
P
I
NP
P
I
I
P
P
P
NP
NP
P
Covalent BondingO If 2 atoms or more form a bond with the
same electronegativity the bonds are nonpolar and they share e- equally. ( F-F )
O If there is an electronegativity difference between bonded atoms, the bonds are polar and e- are pulled toward the more electronegative atom. (H-F)
O If a bond is polar, the molecule will have a slightly negative and slightly positive side, like 2 poles of a magnet.
Video 5.5Molecular Polarity
Molecular PolarityO A polar molecule
will be asymmetrical.
O A nonpolar molecule will have a symmetrical shape or all nonpolar bonds.
Molecular Polarity
Which are polar molecules? Show charges.
- - -
----
-
-
+++
+
++
NP P P
NP NP
Molecular Polarity
Water is polar, and like dissolves like, so only polar
molecules are soluble in water. Polar molecules are
also attracted to an electric field.
Molecular Polarity
O As you can see, normally polar molecules are unaligned.
O When a electric source comes by, the molecules quickly align themselves.
Video 5.6IMF
IMFO Intramolecular forces is another
name for bonds, that keep elements together in compounds.
O Intermolecular forces of attraction are weaker than bonds, but are responsible for holding a substance together (multiple molecules in a confined area).
IMF
O The stronger the IMF, the tighter the structure (solid). The melting and boiling points will be high.
O The weaker the IMF, the looser the structure (gas). The melting and boiling points will be low.
Dipole-DipoleO Dipole-Dipole attractions are strong
forces between polar molecules. It is like static holding the + and – charges together.
Hydrogen Bonding
A special case: Hydrogen Bonds are the strongest bonds between Hydrogen and very electronegative atoms such as F, O and N. (H bonds are FON!) For example, H2O and HF, due to their polarity, they will attract each other.
London Dispersion Forces (LDF)
The weakest attraction between nonpolar molecules occur because electrons temporarily shift creating a temporary + and – charge. The more electrons the compound has, the stronger the force is.
Summary
OFrom weak to strong:ONonpolar LDFOPolar Dipole Dipole forcesOHydrogen bondsOCovalent BondsO Ionic BondsOMetallic Bonds
Class Notes
Show the individual and bonded Lewis structures:
1. Li and F
2. Mg and O
3. Be and S
4. What did all the cations do? 5. What did all the anions do?6. Which of the subatomic particles were changed
and how were they changed?
Type of Bonding?1. CaCl22. CO2
3. H2O
4. BaSO4
5. K2O
6. NaF
7. Na2CO3
8. CH4
9. SO3
10.LiBr11.MgO12.NH4Cl
13.HCl
14.KI15.NaOH16.NO2
17.AlPO4
18.FeCl319.P2O5
20.N2O3