NOTES: CHEMICAL BONDING
CHEMICAL BONDING
PART I: TYPES OF BONDING AND PROPERTIES
IONIC BONDING
• Metal + nonmetal/polyatomic ion
Example: sodium chloride
[pic] [Na] +1 [Cl]-1
Draw Lewis dot structures for:
calcium iodide aluminum fluoride
[Ca]+2 2 [I]-1 [Al]+3 3 [F]-1
OR OR
[Ca]+2 [I]-12 [Al]+3 [F]-13
Properties of ionic compounds:
• Solid at room temperature
• Dissolves in water (dissociate or ionize – break ionic bonds)
• When dissolved, solution conducts electricity
METALLIC BONDING AND METALS:
• metals only! [pic]
delocalized electrons - “sea” of mobile electrons
valence electrons that spread out and move around
randomly from ion to ion
properties of metals:
good conductors of electricity
good conductors of heat
malleable
ductile
luster
NETWORK COVALENT BONDING
covalent crystals
Examples: Quartz (SiO2), diamond (C), graphite (C)
properties:
extremely high melting point/boiling point
do not dissolve
do not conduct electricity
COVALENT COMPOUNDS: POLAR VS. NON-POLAR
nonpolar covalent compound: covalentally bonded compound in which the atoms around the central atom are electrically the same.
dispersion force: weak attraction between molecules
polar covalent compound: covalentally bonded compound in which the atoms/electron pair around the central atom are electrically different
dipole force: attraction between the positive pole of one molecule and the negative pole of another
Properties:
NONPOLAR COVALENT: low melting & boiling points, dissolve in nonpolar solvents such as acetone, strong odors, evaporate easily, does not conduct electricity
POLAR COVALENT: medium melting & boiling points, dissolve in polar solvents, does not conduct electricity
COVALENT BONDING: sharing pairs of electrons
• molecular compounds – non-metals ONLY!
HINTS FOR DRAWING DOT DIAGRAMS FOR MOLECULAR COMPOUNDS
Steps
1. count the total number of valence electrons
2. choose a central atom (normally the first atom unless the 1st is hydrogen. Then choose 2nd atom.)
3. Arrange other atoms around central atom
4. Place a pair of electrons between adjacent atoms
5. Place remaining electrons to make sure every atom is stable (H – 2, most others – 8)
HINTS: C always in the center, always bonds 4x
H, halogens never in center, always bond 1x
O unless an ion, bonds 2x
N usually bonds 3x
|H2 |Cl2 |
|[pic] |[pic] |
|H2O |CH4 |
|[pic] |[pic] |
|NH3 |O2 |
|[pic] |[pic] |
|N2 |CH2O |
|[pic] |[pic] |
|CO2 |HCN |
|[pic] |[pic] |
|SO2 |C2F2 |
|[pic] |[pic] |
|NO3-1 |SO4-2 |
|[pic] |[pic] |
| | |
| | |
| | |
|NH4+1 |O3 |
|[pic] |[pic] |
| | |
VSEPR THEORY – Place electrons as far away from each other as possible to minimize repulsion
|EXAMPLE |LEWIS |XY |3D DIAGRAM |ANGLE/ |
| |DIAGRAM |NOTATION | |GEOMETRY |
| | | |[pic] |Linear |
|HCl |[pic] |XY | |180º |
| | | | | |
| | |diatomic molecule | | |
| |[pic] | | |Linear |
|CO2 | |XY2 No lone pair! |[pic] |180º |
| | | | | |
| | |2 atoms attached to central atom | | |
| |[pic] | |[pic] |Trigonal Planar |
| | |XY3 No lone pair! | |120º |
|BF3 | | | | |
| | |3 atoms attached to central atom | | |
| |[pic] | |[pic] | |
| | |XY4 No lone pair! | |Tetrahedral |
|CH4 | | | |109.5º |
| | |4 atoms attached to central atom | | |
| |[pic] | |[pic] |Pyramidal |
| | |XY3E (E=electron pair) | |(Trigonal Pyramidal) |
|NH3 | | | | ................
................
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