covalent compounds contain 2 or more nonmetals. made of molecules—not ions. 2 nonmetals can...
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Covalent Compounds• Contain 2 or more nonmetals.
• Made of molecules—NOT IONS.• 2 nonmetals can combine in more than 1 way!
• CO2 is a gas that we breathe out.• CO is a colorless, odorless, & deadly gas
• Both are carbon oxides, but it is important to distinguish between them.
Naming Covalent• The number of each element (subscript) is written as
a prefix in the both parts of the name.• Change the ending to –ide on the 2nd element
1-mono2-di3-tri4-tetra5-penta
6-hexa7-hepta8-octa9-nona10-deca
Examples: CO2 is carbon dioxideCO is carbon monoxide
IMPORTANT: The mono prefix is omitted only on the first element.*On the back of your P.T.
Formulas of Covalent
• The prefixes on each element tell you the subscripts in the formula
• Example: tetraiodine nonoxide• I4O9
Lets try some examples• Given the formula, name the following molecular
compounds.• N2O
• Dinitrogen monoxide
• PCl3• Phosphorus trichloride
• SF6
• Sulfur hexafluoride
• CS2
• Carbon disulfide
More examples• Given the name, what’s the formula for the following
compounds.• Nitrogen trifluoride
• NF3
• Disulfur dichloride• S2Cl2
• Dinitrogen tetroxide• N2O4
• Phosphorus pentafluoride• PF5
Molecular Compounds• Molecular = Covalent• In a covalent bond, electrons are shared• Diatomic molecule—a molecule consisting of 2
atoms• Hydrogen = H2
N2 O2 F2 Cl2 Br2 I2
Properties• Have lower melting/boiling points than ionic• Most are gases or liquids at room temp.
• Composed of 2 (or more) nonmetals
• When writing a molecular formula, the subscripts are not always in the lowest ratio.• Ex. H2O2
Covalent Bonding• Molecules can form single, double, and triple bonds• Single: share 1 pair of e- (2 e-)
• Shown as a single line• Double: share 2 pairs of e- (4 e-)
• Shown as a double line• Triple: share 3 pairs of e- (6 e-)
• Shown as a triple line
Acetone
Bond Strength• Many covalent compounds are more stable
than the atoms alone.• Bond Dissociation Energy—the energy
required to break the bond between 2 covalently bonded atoms
• A large dissociation energy corresponds to a strong covalent bond
Bonding Theories
• VSEPR Theory:• Valence Shell Electron Pair Repulsion
• The repulsion between e- pairs causes the shape of molecules to adjust so e- pairs are as far apart as possible
Molecular Shapes Linear Trigonal
PlanarBent
Pyramidal Tetrahedral Trigonal Bipyramidal
Octahedral Square Planar
T-Shaped
Polarity and Molecules• Covalent Bonds can be polar or nonpolar• Nonpolar—formed when e- are shared equally
between 2 atoms• Bonds can be nonpolar in 2 ways
• Nonpolar covalent bonds• Ex. Diatomic elements: H2 N2 O2 F2
• Polar Bonds due to symmetry• CH4
Polar Bonds• Formed when e- are shared unequally between 2 atoms• The more electronegative atom attracts e- more
strongly and gains a slightly negative charge• The less electronegative atom has a slightly positive
chargeElectronegativity Differences & Bond Types
Electronegativity Difference Range
Bond Type
0.0-0.4 Nonpolar Covalent
0.4-1.0 Slightly Polar Covalent
1.0-2.0 Very Polar Covalent
≥2.0 Ionic
Characteristics of Ionic & CovalentCharacteristic Ionic Covalent
Representative unit Formula Unit Molecule
Bond formation e- transfer (gained or lost)
e- shared
Type of elements Metal + Nonmetal (& polyatomic ions)
Nonmetal + Nonmetal
Physical state Solids Solid, liquid, gas
Melting Point High Low
Solubility in water High High to Low
Electrical conductivity in aqueous solution
Good conductor Poor to nonconducting
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