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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