Noble gas configuration is the term given to the electron configuration of noble gases. The basis of all chemical reactions is the tendency of chemical elements to acquire stability. For some main group elements, chemical bond formation often results in a complete electronic configuration resembling a noble gas.
Noble gas configuration Wikipedia
W. Kossel and Gilbert N. Lewis saw that noble gases did not have the tendency of taking part in chemical reactions under ordinary set of conditions. On the basis of this observation they concluded that atoms of noble gases are stable and on the basis of this conclusion they proposed a theory of valency known as "Electronic Theory of valency" in 1916:
During the formation of a chemical bond, atoms combine together by gaining, losing or sharing electrons in such a way that they acquire nearest noble gas configuration.
Every system has the tendency to acquire the state of stability or a state of minimum energy, and so chemical elements take part in chemical reactions to acquire a stable electronic configuration similar to that of its nearest noble gas. An example of this tendency is hydrogen'(H)s reaction with oxygen(O) to form water(H2O). Hydrogen in ground state has the Valency 1 and on formation of water it acquires a stable valency of 2, similar to that of its nearest noble gas helium. Nevertheless, a lot of chemical elements especially transition elements can achieve stability with other configurations.