Compound connection or complex connection or complex joint is the formation of a chemical compound by the union of two or more chemical species. When simple components react chemically to product complex components these are called compound connections.

* Formation of Ammonia (NH3)

$$N_2 + 3H_2 \longrightarrow 2NH_3$$

In this reaction , nitrogen (N2) and hydrogen (H2) molecules react to form a new compound called Ammonia(NH3).

* Formation of Water (H2O)

$$2H_2 + O_2 \longrightarrow 2H_2O$$

In this reaction, hydrogen(H2) and oxygen (O2) molecules react to form a new compound called water (H2O).