In these reactions, an atom/ion present in a compound gets replaced by an atom/ion of another element.
Example: FeSO4 + Zn → ZnSO4 + Fe
Combination reaction:
In these reactions, compounds are formed as a result of the chemical combination of two or more elements.
Example: C + O2 → CO2 ; 2Cu + O2 → 2CuO
Decomposition reaction:
In these reactions, compound either of its own or upon heating decomposes to given two or more components out of which at least one is in the elemental state.
Example: 2NaH → Na + H2.
Double displacement creation:
In these reactions, two compounds exchange ions to form two new compounds.
Example: Na2S + 2HCL → 2NaCl + H2S.
Precipitation:
It is any form of solid or liquid particles that are released from the atmosphere or clouds in the form of rain, freezing rain, sleet, snow, or hail.