Molecular Compounds- Covalent Bonding
Molecular compounds are created when two or more unstable non-metals chemically react with each other to obtain stable valence shells. It is easier for non-metals to gain valence electrons to obtain a full valence shell since they have at least 4,5,6 or 7. When two _______________react, both want to have full valence shells but neither want to donate valence electrons. The only happy medium is if both______ the valence electrons they have amongst each other.
The type of chemical bond that exists through sharing of valence electrons between ____________ is called a _____________________.

Because there is no exchange of valence electrons, only sharing, no ions are formed (no criss-
cross rule)
 valence electrons shared between the two non-metals
Lets show this bonding using Bohr-Rutherford diagrams
* remember: the number of valence electrons an atoms has lets you know how many it needs to obtain a full valence shell.
Properties: They are 3-D compounds that can be solids, liquids or gases. They have low melting points and boiling points compared to ionic compounds. Most do not easily dissolve in water. They do not conduct electricity when dissolved in water.
Diatomic Compounds

Some elements are too reactive (unstable) to exist on their own
 these elements are non-metals and will combine with themselves by sharing valence electrons so each can have full valence shells (full octet)
 the following elements always form diatomic compounds when they are combining with other elements
HOFBrICl

Element
Hydrogen
Oxygen
Fluorine
Bromine
Iodine
Nitrogen
Chlorine
Chemical Formula
Naming molecular compounds-use prefixes
Some molecular compounds are always known by their common name
H
2
O -____________
NH
3
- ____________
H
2
O
2
-____________
CH
4
-_____________

Most molecular compounds are named using a prefix system
 prefixes are used to indicate the number of atoms in the compound (no criss-cross rule)
 the prefix is placed in front of the name of the element you are emphasizing
1.
The atom closest to the bottom left corner of the periodic table is named first.
2.
The atom closest to the top right is named second.
Prefix
Mono
Di
Tri
Tetra
Penta
Hexa
Number
1
2
3
4
5
6 ex As
2
O
3
Both are non-metals, therefore we use prefixes: diarsenic trioxide
SIO
2
NO
2
N
2
SiH
4
PCl
P
2
S
3
3

Li
2
O
Writing Formulas for Molecular Compounds

The prefixes used tell you exacty the number of atoms in the formula

There are no ions and no criss-cross rule used ex. diphosphorus pentoxide
2- phosphorus 5-oxygens : P
2
O
5
Carbon tetrabromide
Diboron trioxide
Dinotrogen monixide
Iodine hexafuoride
Oxygen
Carbon terahydride