In which year did Langmuir reform the Lewis concept by abandoning the idea of a stable cubical arrangement of the octet and introducing the term ‘covalent bond’?

Explanation

NCERT dates Langmuir’s refinement of the Lewis account and introduction of covalent-bond terminology to 1919. Langmuir’s 1919 paper, The Arrangement of Electrons in Atoms and Molecules, is part of that historical development. The modern quantum description of bonding developed beyond these early octet models.