1. Molecules and Molecular Compounds
Section 2.6
Molecules and Molecular Compounds

2. Remember…
Atoms are the smallest representative sample of an element Building Blocks of Matter!
BUT- only the noble gases are found as isolated atoms
The rest exist as molecules or ions

3. Molecules
Assembly of two or more atoms tightly bound together, behaving as a single object

4. Chemical Formula
Notation that uses chemical symbols and subscript notation to convey relative proportions of atoms of elements in a molecule

5. Diatomic Molecule Molecule composed of two atoms
Elements normally occurring as diatomic:
Hydrogen (H2)
Oxygen (O2)
Nitrogen (N2)
The halogens (F2, Cl2, Br 2, I2)

6. Most molecular compounds contain only nonmetals!!
Compounds composed of molecules
Contain more than one type of atom
Examples: CH4, H2O, H2O2
Most molecular compounds contain only nonmetals!!

8. Molecular Formula
Indicate the actual numbers and types of atoms in a molecule.
Empirical Formula
Only give the relative number of atoms of each type in a molecule.
Subscript is always the smallest possible whole-number ratio

9. Examples

11. Now You Try…

14. Does the converse hold true?
If we know the molecular formula, we can determine the empirical formula!
Does the converse hold true?

15. Structural Formula
Shows which atoms are attached to each other within a molecule
Atoms are represented by their chemical symbol
Lines represent bonds
Do not depict the geometry of the molecule (the angles of the bonds)

16. Acetone

17. Perspective Drawings
Structural formula that gives a sense of the three-dimensional shape of a molecule
Methane

18. Ball-and-stick models
Shows atoms as spheres and bonds as sticks
Accurately represents angles of the bonds
Also demonstrates relative size of atoms
Water

19. Space-filling models Water Depict a molecule scaled up to size
Show relative size of atoms
Difficult to see the angles of the bonds
Water