Question

Until the early 1960s, the group 8A elements were called the inert gases. (a) Why was the term inert gases dropped? (b) What discovery triggered this change in name? (c) What name is applied to the group now?

Short answer

The term "inert gases" was dropped because the discovery by chemist Neil Bartlett in the early 1960s showed that xenon, one of the inert gases, could form compounds under specific conditions, contradicting the belief that these elements were entirely unreactive. The group 8A elements are now called "noble gases," which reflects their general unreactivity and extraordinary properties, while acknowledging their ability to form compounds under certain conditions.

Step-by-step solution

Understanding the term "inert gases"

Before the 1960s, the group 8A elements (helium, neon, argon, krypton, xenon, and radon) were called inert gases. This term was used because these elements were believed to be chemically inactive, i.e., they did not undergo chemical reactions with other elements. This belief was due to the full valence electron shells in these elements, which made them stable and unreactive.

What discovery triggered the change in name?

In the early 1960s, a significant breakthrough in chemistry occurred when chemist Neil Bartlett discovered that xenon, one of the inert gases, could, under specific conditions, form compounds with other elements. He synthesized the first noble gas compound, xenon hexafluoroplatinate (XePtF_6). This discovery contradicted the prevailing belief that the inert gases were entirely unreactive and could not form compounds.

Why was the term inert gases dropped?

In light of Bartlett's discovery, it became clear that the group 8A elements were not entirely chemically inactive, as previously thought. As a result, the term "inert gases" was deemed inaccurate and misleading. Chemists recognized that these elements could undergo chemical reactions under specific conditions and form compounds. Thus, the term "inert gases" was no longer suitable for describing these elements.

The current name for the group 8A elements

The group 8A elements are now commonly known as the "noble gases." The name "noble" implies that these elements are rare and possess some extraordinary properties (e.g., their low reactivity and tendency to exist in a monatomic state in the natural environment). This new name reflects the updated understanding of their properties and behavior, considering that they can form compounds under certain conditions, although they remain generally unreactive compared to other elements.

Key concepts

Inert Gases

Originally known as 'inert gases', the elements in group 8A of the periodic table were thought to be completely unreactive due to their full outer electron shells. This feature makes them very stable, as the full valence electron configuration provides little incentive for these atoms to engage in chemical reactions.

However, the term 'inert' suggests an absolute inability to participate in chemical processes, which, as scientific research later revealed, is not the case for these gases. Despite their high stability, certain noble gases can indeed form compounds under the right conditions. Therefore, to prevent misunderstanding, the scientific community moved away from the term 'inert gases' in favor of a more accurate descriptor.

Group 8A Elements

The group 8A elements, also known as the noble gases, encompass helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).

These elements are colorless, odorless, nonflammable, and monatomic in their natural state, which means they exist as individual atoms rather than molecules. Their unique characteristics arise from their electron configurations, as each (except helium) has eight electrons in its outer shell, giving them particular stability and influencing their low chemical reactivity.

Chemical Reactivity

Chemical reactivity refers to the propensity of a substance to undergo a chemical reaction with another substance. Factors influencing reactivity include electron configurations, ionization energy, and the presence of unfilled electron shells.

Noble gases are renowned for their low chemical reactivity, primarily because their full outer electron shells minimize their tendency to gain or lose electrons. However, under certain circumstances, such as exposure to high pressures or the presence of highly reactive substances, noble gases can be coaxed into forming compounds, as seen in the historic synthesis of xenon hexafluoroplatinate.

Noble Gas Compounds

The synthesis of noble gas compounds contradicted the formerly held belief that these elements were entirely unreactive. Neil Bartlett's groundbreaking work demonstrated that noble gases could indeed form stable compounds, although it often requires extreme conditions or highly reactive partners.

Examples of these compounds include xenon difluoride (XeF₂) and xenon hexafluoride (XeF₆), both of which are fluorides of xenon, a noble gas previously thought to be incapable of forming chemical bonds. These compounds have unique properties and applications, from use in advanced lighting to their roles as oxidizing agents in chemical reactions.