1. Molecular Compounds

2. Objectives
Distinguish between the melting points and boiling points of molecular compounds and ionic compounds
Describe the information provided by a molecular formula

3. Important Vocabulary Covalent bond Molecule Diatomic molecule
Molecular compound
Molecular formula

4. Molecules Matter takes may forms in nature
Noble gas elements exist as single atoms (monatomic)
Some atoms of elements form salts that are crystalline solids with high melting points
Many atoms form molecules, which are neutral groups of atoms joined together by covalent bonds
A covalent bond is formed when two atoms share electrons

5. Sharing Electrons
Takes place between neutral atoms within covalent compounds
Attractive and repulsive forces must be equal for a bond to form
The simplest example of this is found in diatomic molecules, which are molecules consisting of two atoms
What seven elements are diatomic?
HINT: HI BrONClF

6. Molecular Compounds Molecular compounds are composed of molecules
The molecules of a given molecular compound are all the same
For example: water (dihydrogen oxide) & carbon monoxide
They are also known as covalent compounds because they form covalent bonds

7. Molecular Compound Properties
Molecular compounds tend to have relatively lower melting and boiling points
Most are liquids or gases at room temperature
Most molecular compounds are composed of atoms of two or more nonmetals

8. Ionic Compounds vs. Covalent Compounds

9. Molecular Formulas
A molecular formula is the chemical formula of a molecular compound
A molecular formula shows how many atoms of each element a molecule contains
For example: A water molecule consists of 2 hydrogen atoms and 1 oxygen atoms, so its molecular formula is H2O
What doesn’t a molecular formula tell us?

10. Practice
How many atoms of each?
C2H6
CO2
CCl4