Transcript Covalent Bonding

Chemical Bonding
Covalent / Molecular
Compounds
I
II
III
IV
Properties of Covalent Bonds
Bond Formation
Type of Structure
Electrons shared
between two nonmetals
True Molecules
Physical State
Liquid or Gas
Melting Point
Low
Solubility in Water
Usually not
Electrical Conductivity
No
Other Properties
Odorous
Bond Polarity
Nonpolar Covalent Bond
e- are shared equally
symmetrical e- density
usually identical atoms
Nonpolar Covalent Molecules
The Seven Diatomic Elements
Br2 I2 N2 Cl2 H2 O2 F2
H
N O F
Cl
Br
I
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.
Bond Polarity
Examples:
Cl2
3.0-3.0=0.0
Nonpolar
HCl
3.0-2.1=0.9
Polar
NaCl
3.0-0.9=2.1
Ionic
Lewis Structures
Nonpolar Covalent - no charges
Polar Covalent - partial charges
+
+
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.
Molecular Nomenclature
PREFIX
monoditritetrapentahexaheptaoctanonadeca-
NUMBER
1
2
3
4
5
6
7
8
9
10
Molecular Nomenclature
CCl4
carbon tetrachloride
N2O
dinitrogen monoxide
SF6
sulfur hexafluoride
Molecular Nomenclature
arsenic trichloride
AsCl3
dinitrogen pentoxide
N2O5
tetraphosphorus decoxide
P4O10
Metallic
Bonding
Properties of Metallic Bonds
METALLIC
Bond
Formation
e- are delocalized
among metal atoms
Type of
Structure
“electron sea”
Physical
State
solid
Melting
Point
very high
Solubility in
Water
no
Electrical
Conductivity
yes
(any form)
Other
Properties
malleable, ductile,
lustrous
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
Intermolecular
Forces
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 forces
Exists between identical atoms
Dipole-dipole forces
Attractions between oppositely charged
regions of polar molecules
Stronger than dispersion forces
Exists 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
Hydrogen bonding
Properties of Hydrogen Bonding
Stronger forces=higher melting/boiling
points
Weaker forces=lower melting/boiling
points