1. Molecular Compounds 3.3

2. Facts Molecular compounds occur when non metals combine to form a pure compound. These non-metals share electrons forming a molecular bond (or covalent bond). The sharing of electrons creates a stable outer shell. Molecular compounds can be solids liquids or gases at room temperature.

3. Properties They are insulators. They have a low melting point The forces or bonds holding the molecules together are weak.

4. Strength of the Bond Varies 1.A single covalent bond is created when two atoms share a pair of electrons.. Example HI 2.A double bond is stronger and is formed when two atoms share two pairs (4) of electrons. Example 02- oxygen gas 3.For a triple bond, two atoms share three pairs of electrons.

5. Writing Formulas for a Molecular Compound This is similar to ionic compounds except we do not use the ion charge. Ex Hydrogen is found in nature as a diatomic element H2. This means each molecule has two atoms of hydrogen connected to it. For ammonia NH3, the situation is similar so we have 3 H combining with 1 N

6. Naming Molecular Compounds All molecular compounds except those that contain H can be named using the following rules. For these we will use their common name.

7. Rules Page 152 1. The first element of the compound uses the element name 2. The second element has the suffix “ide” 3. When there is more than one atom in the formula, prefixes are used to indicate the number of each atom. 4. Exception is if only one atom of an element is used. In this case we don't use the prefix “mono”

8. List of Prefixes 1Mono6hexa 2Di7 hepta 3Tri8octa 4Tetra9nona 5Penta10deca Our formula based on these rules: prefix + element prefix + second element (ide) prefix + element prefix + second element (ide)

9. Examples Carbon dioxide CO 2 dinitrogen monoxide N 2 O Water H 2 O

10. EXAMPLES 1. N 2 O 3 2. CCl 4

11. Examples 3. tetraphosphorus trisulfide 4.nitrogen trioxide

12. Compare molecular and ionic compounds http://www.youtube.com/watch?v=yjge1WdCFPs

13. Comparing Ionic and Molecular Compounds Ionic CompoundsMolecular CompoundsProperty Conduct Electricity Low Boiling point Solid at room temperature Distinct crystal shape Composed of two non metals

14. Practice Check and Reflect on Page 153