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Properties of Covalent Bonds
Bond Formation Electrons shared between two nonmetals
Type of Structure True Molecules
Physical State Liquid or Gas
Melting Point Low
Solubility in Water Usually not
Electrical Conductivity No
Other Properties Odorous
Nonpolar Covalent Bond e- are shared equally symmetrical e- density usually identical atoms
Bond Polarity
+ -
Bond Polarity
Polar Covalent Bond e- are shared unequally asymmetrical e- density results in partial charges (dipole)
Bond Polarity
Remember, most bonds are a blend of ionic and covalent characteristics.
Difference in electronegativity determines bond type.
Naming Covalent Compounds
Prefix System (binary compounds)
1. Less e-neg atom comes first.
2. Add prefixes to indicate # of atoms. Omit mono- prefix on first element.
3. Change the ending of the second element to -ide.
arsenic trichloride
dinitrogen pentoxide
tetraphosphorus decoxide
AsCl3
N2O5
P4O10
Molecular Nomenclature
“electron sea”
METALLICBond Formation
Type of Structure
Solubility in Water
Electrical Conductivity
OtherProperties
MeltingPoint
Properties of Metallic Bonds
Physical State
e- are delocalized among metal atoms
very high
yes (any form)
no
malleable, ductile, lustrous
solid
Metallic Bonds
Metal atoms are held together in the solid through metallic bonding.
Metals hold on to their valence electrons very weakly.
Think of them as positive ions (cations) floating in a sea of electrons.
Sea of Electrons
+ + + ++ + + +
+ + + +
Electrons are free to move through the solid.
This is why metals are able to conduct electricity.
Metals are…
Metals are malleable - hammered into shape (bend).
Also ductile - drawn into wires.Both malleability and ductility
demonstrate the mobility of the valence electrons
Intramolecular vs Intermolecular
Intramolecular - forces that hold particles together in ionic, covalent and metallic bonds
Intermolecular - attractions between one molecule and a neighboring molecule.
Intermolecular Forces
Types of intermolecular forces: Dispersion forces Dipole-dipole Hydrogen bonds
Dispersion forces
Weak forces that result from temporary shifts in the density of electrons in electron clouds, creating an induced dipole.
Weakest of the intermolecular forcesExists between identical atoms
Dipole-dipole forces
Attractions between oppositely charged regions of polar molecules
Stronger than dispersion forcesExists between polar covalent molecules
Hydrogen bonding
Special type of dipole-dipole attraction that occurs between molecules containing a hydrogen atom bonded to a small, highly electronegative atom with at least one lone electron pair.
Occurs between hydrogen and either fluorine, oxygen, and nitrogen atoms only.
Strongest of the forces