Langmuir's Contribution to Covalent Bonding: The Year of Reform

The question asks about the specific year when Irving Langmuir modified Gilbert N. Lewis's concept of chemical bonding. Lewis had proposed the idea that atoms achieve stability by forming an octet (eight electrons) in their outermost shell, often picturing these electrons arranged at the corners of a cube. This was known as the Lewis cubical octet concept.

While Lewis introduced the concept of sharing electron pairs, which laid the groundwork for understanding covalent bonds, Langmuir built upon this foundation. Langmuir refined Lewis's ideas by moving away from the rigid, static cubical model for electron arrangement. More significantly, Langmuir coined the term "covalent bond" to describe the linkage formed by the mutual sharing of electrons between atoms.

Langmuir's work in this area was highly influential and helped solidify the understanding of chemical bonds formed by electron sharing. His publication detailing these refinements, including the introduction of the term 'covalent bond' and abandoning the stable cubical arrangement idea, occurred in a specific year that marked a key step in the development of chemical bonding theory.

Based on historical accounts of the development of chemical bonding theories, Irving Langmuir published his significant paper titled "The Arrangement of Electrons in Atoms and Molecules" in which he introduced the term 'covalent bond' and elaborated on the sharing of electrons, in 1919.

Let's look at the given options:

1. 1919
2. 1915
3. 1921
4. 1917

Comparing this information with the options provided, the year 1919 is the correct year when Langmuir made these significant contributions to the understanding of the covalent bond, building upon Lewis's earlier work.

Revision Table: Key Milestones in Chemical Bonding

Additional Information: Expanding on Covalent Bonds and Octet Rule

The concept of the covalent bond is fundamental to chemistry. It explains how nonmetal atoms typically bond with each other by sharing valence electrons to achieve a stable electron configuration, often resembling that of a noble gas (the octet rule).

• Lewis Structures: These diagrams, introduced by Lewis, use dots to represent valence electrons and lines to represent shared pairs (covalent bonds). They are simple tools for visualizing bonding and electron arrangement in molecules.
• Octet Rule: The tendency of atoms to gain, lose, or share electrons until they are surrounded by eight valence electrons is known as the octet rule. While widely applicable, there are exceptions, particularly for elements in the third period and beyond, and for molecules with an odd number of valence electrons.
• Evolution of Bonding Theories: The ideas of Lewis and Langmuir were foundational but were later explained more rigorously by quantum mechanics, leading to theories like Valence Bond Theory and Molecular Orbital Theory, which provide deeper insights into bond formation, bond strength, and molecular geometry.

Langmuir's contribution in 1919 was crucial because it provided a more accurate description of the covalent bond and a more flexible way to think about electron arrangements compared to the earlier rigid models.