Atoms and Molecules: Formula Sheet
Atoms and molecules are fundamental concepts in chemistry. Here’s a concise formula sheet to help you understand the key concepts.

1. Atomic Mass
- Atomic mass is the weighted average mass of an atom of an element.
- Measured in atomic mass units (amu).

2. Mole Concept
- 1 mole = \(6.022 \times 10^{23}\) particles (Avogadro's number).
- Molar mass = mass of one mole of a substance (g/mol).

3. Chemical Formula
- Represents the composition of a compound.
- Empirical formula: simplest whole-number ratio of elements.
- Molecular formula: actual number of atoms of each element in a molecule.

4. Law of Conservation of Mass
- Mass of reactants = Mass of products.

5. Balancing Chemical Equations
- Ensure the number of atoms of each element is the same on both sides.
- Use coefficients to balance the equation.

6. Types of Chemical Reactions
- **Synthesis Reaction**: A + B → AB
- **Decomposition Reaction**: AB → A + B
- **Single Displacement Reaction**: A + BC → AC + B
- **Double Displacement Reaction**: AB + CD → AD + CB

7. Mole Calculation
- Number of moles = \(\frac{\text{Given mass (g)}}{\text{Molar mass (g/mol)}}\)

8. Concentration of Solutions
- Concentration (C) = \(\frac{\text{Number of moles of solute}}{\text{Volume of solution in liters}}\)

9. Percentage Composition
- Percentage of element in a compound = \(\frac{\text{Mass of element in 1 mole of compound}}{\text{Molar mass of compound}} \times 100\)
This formula sheet provides a solid foundation for the chapter on atoms and molecules, crucial for understanding basic chemistry principles.