Molecular Compounds

Covalent Bonding:

Ionic compounds combine in a simplest formula ratio (I.e. CaO, not Ca2O2)
This is not true of nonmetals bonding with each other. Ex. CH is a simplest formula ratio of carbon and hydrogen, but there are many chemical compounds that have this formula ratio, but each compound exhibits very different chemical properties. Ex. Ethyne gas (C2H2) and liquid benzene (C6H6)
Simplest formula ratios indicate only the relative number of atoms in a molecular compound, but no information about the actual number of atoms or the arrangement of those atoms in a molecule
Lewis structures and structural diagrams are two tools that can be used to represent covalently bonded molecules.

Formation of Covalent Bonds:

Covalent bond is the bond that arises from the simultaneous attraction of two nuclei for a shared pair of electrons
The electron dot diagram used in covalent bonding is called an electron dot structure because it represents the free valence electrons as dots and the shared pair of electrons as a line.
Ex. Cl + Cl

Structural diagrams further simplify the lewis structural diagram by not representing the lone pairs (unshared) electrons and only representing the shared electrons as a dash.
Ex. Br + Br

Ex. O + O

Bonding Capacity:

The number of covalent bonds (shared electron pairs) that an atom can form is known as its bonding capacity.

Atom
Valence Electrons
Bonding Electrons
Bonding Capacity
C

N

O

Halogens

Hydrogen

Structural formulas typically place the atom with the highest bonding capacity at the center of the arrangement. Ex. CO2, H2O

Electronegative elements are less likely to be the central atom in a bonding arrangement

Naming Molecular Compounds:

First non-metal is written with is proper name, the second non-metal receives the suffix –ide.
Greek prefixes are used to indicate the number of atoms for each element in that molecule
Common prefixes can be found on p. 97, Table 5
If there is only one of the first type of atom, the prefix mono- is omitted.
Ex. CF4

Exception is hydrogen which commonly does not use the prefix system and is instead always written as hydrogen.

Covalent Bonds:

Many substances contain a combination of covalent and ionic bonding. Ex. NH4Cl
Coordinate Covalent bond – covalent bond where both of the electrons making up