Atoms and Molecules

1. 3. What is a Molecule

1.1. Molecules of elements

1.2. Molecules of compounds

1.3. ions

2. 4. Writing Chemical Formulae

3. 5. Molecular Mass and Mole Concept

3.1. Molecular Mass

3.2. Formula Unit Mass

3.3. Mole Concept

4. 1. Laws of Chemical Combination

4.1. Law of conservation of mass

4.2. Law of Constant Proportion

5. 2. What is an Atom

5.1. Symbols

5.2. Atomic Mass

5.3. How do they exist?