1. Combination reaction: Two or more substances combine to form a single product.

Example: 2H2 + O2 → 2H2O

2. Decomposition reaction: A single substance breaks down into two or more products.

Example: 2H2O → 2H2 + O2

3. Single-replacement reaction: One element replaces another element in a compound.

Example: Zn + 2HCl → ZnCl2 + H2

4. Double-replacement reaction: Two compounds exchange ions to form two new compounds.

Example: NaCl + AgNO3 → NaNO3 + AgCl