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The Covalent Bond and Molecular Compounds
Chemistry
Mrs. Coyle
The Periodic Table and Atomic Radius
Types of Bonds
Ionic Metallic Covalent
The Covalent Bond
• The bond in which atoms are held together by their mutual electrical attraction for shared electrons.
Fluorine
Movie Clip
http://www.youtube.com/watch?v=Kj3o0XvhVqQ&NR=1
The Covalent Bond
A single covalent bond is made up of two electrons.
The covalent bond is represented using a straight line.
F — FF F
Molecule
A neutral group of atoms joined together by covalent bonds.
Diatomic Molecules
Molecules made up of two atoms.
There are 7 diatomic molecules.
H2, N2, O2, F2, Cl2, Br2, I2
Hydrogen
H· + ·H H:HHydrogen Hydrogen Hydrogen
Atom Atom molecule
The hydrogen molecule has a single covalent bond.
The electronegativity of each hydrogenatom is the same, so the electrons are shared.
Shared electron pair
Molecular Compounds
Compounds comprised of molecules.
Ionic Compounds Molecular Compounds
Crystal Lattice Molecule
Types of Elements
Metal with non-metal or polyatomic ions
Non-metal with non-metal
Physical State
Solid Solid, liquid or gas
Melting Point High
> 300 CLow
<300 CSolubility in water
Generally high Generally low
Electrical conductivity of solution
Good conductor Poor to none
Molecular Formula
A molecular formula is a chemical formula that is used for molecular compounds.
It shows the types and number of atoms in a molecule.
Note that ionic compounds used the chemical formula called the formula unit.
A molecular formula does not give information about the molecules structure.
Structural Formula
Structural formulas show the arrangement of atoms in a molecule.
In a structural formula, the electron pair is represented by a line
Example: H-H
(single bond: one pair of electrons)
Space Filling Model
Methane
CH4
Ball and Stick Models
Ethane
C2H6
The Water Molecule
•
The Ammonia Molecule
.
NH3