Section 6-2 Covalent Bonding and Molecular Compounds

Molecule: a neutral group of atoms that are held together by covalent bonds

Molecular compound: a chemical compound whose simplest units are molecules

Chemical Formula: shows relative numbers of atoms in a compound by using atomic symbols
and subscripts

Molecular Formula: shows types and numbers of atoms combined in a single molecule

Diatomic Molecule: molecule only containing two atoms
A. Formation of a Covalent Bond
I. As two atoms approach, their charged particles interact
II. Nuclei and Electrons begin to attract each other
III.Electrons/Electrons and Nuclei/Nuclei begin to repel each other
IV.
At a specific distance, the attraction outweighs the repulsion.
B. Characteristics of the Covalent Bond
I. Bond Length: The distance between atoms that leads to the minimum potential energy
between the atoms (Hydrogen – Hydrogen bond length = 75pm)
II. Bond Energy: The energy required to break a chemical bond and form neutral, isolated
atoms. (Hydrogen – Hydrogen Bond Energy = 436kJ needed)
III.Bond Energy is inversely proportional to Bond Length: The larger the bond energy, the
smaller the bond length.
C. The Octet Rule (Orbital Basis for Bond Formation)
I. Covalent Bonding occurs due to the overlap of valence orbitals
II. Octet Rule: Chemical compounds tend to form so that each atom by gaining, losing, or
sharing electrons, has an octet of electrons in its highest occupied energy level.
a. F2 = Fluorine Molecule = F – F
b. HCl = Hydrogen Chloride Molecule = Hydrochloric Acid = H – Cl
D. Lewis Structures
E. Multiple Covalent Bonds
F. Resonance Structures
I. Some molecules and ions cannot be represented adequately by a single Lewis structure.
II. Examples:
a. Ozone = O3 = O – O – O
b. Nitrogen Dioxide = NO2 = O – N – O
G. Covalent Network Bonding
I. Non-molecular covalently bound atoms.
II. Bonding that continues “infinitely” in all(or most) directions
III.Examples include Diamonds and Carbon Nanotubes