Question

State and explain the evidence which reveals that the outer shell of each inert gas atom is full.

Short answer

Inert gases have full outer electron shells, as shown by their electron configurations and minimal chemical reactivity.

Step-by-step solution

Understanding Inert Gases

Inert gases, also known as noble gases, are located in Group 18 of the periodic table. These include helium, neon, argon, krypton, xenon, and radon. Their chemical inertness originally suggested that their outer electron shells are complete.

Analyzing Electron Configuration

The electronic configuration of inert gases shows a complete outer electron shell. For instance, helium has an electron configuration of 1s², meaning its only shell is filled. Neon, with a configuration of 1s² 2s² 2p⁶, has a filled valence shell with 8 electrons in the second shell.

Exploring Octet Rule

The octet rule states that atoms tend to have eight electrons in their valence shell, achieving a stable electron configuration similar to that of noble gases. Each inert gas (except helium) has fulfilled this rule, which is evidence for their full outer electron shell.

Considering Chemical Inactivity

Noble gases are known for their lack of reactivity. Their complete outer shells mean they do not tend to gain, lose, or share electrons, resulting in minimal chemical bonding under normal conditions. This inaction infers that the outer shell is full and stable.

Key concepts

Electron Configuration

Understanding electron configuration is key to comprehending why noble gases, or inert gases, are considered chemically stable. The electron configuration of an atom describes the distribution of electrons in its atomic or molecular orbitals. It's a concise way to represent how electrons occupy these orbitals.
For noble gases, their electron configuration reveals that each atom has a complete outer electron shell.

• Helium, with a configuration of 1s², has its only shell completely filled with two electrons.
• Neon follows with a configuration of 1s² 2s² 2p⁶, indicating a full second shell.

Other noble gases like argon, krypton, xenon, and radon, continue this pattern with fully filled orbitals among their outermost shell, aligning with their positions in Group 18 of the periodic table.
This completeness is a fundamental characteristic that significantly influences their non-reactiveness.

Octet Rule

The octet rule is a principle that plays a crucial role in explaining the stability of noble gases. It states that atoms are generally more stable when they have eight electrons in their valence (outermost) shell. This configuration resembles that of noble gases, like neon or argon, and is energetically favorable.

• Most elements will gain, lose, or share electrons to achieve a valence shell resembling a noble gas, often attaining a "pseudo-noble gas" configuration.
• Noble gases naturally obey the octet rule, which is why they have little tendency to interact or form bonds with other elements.

An exception to this rule is helium, which achieves stability with just two electrons. The octet rule helps to explain why noble gases are used as a benchmark for chemical stability across the periodic table.

Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom. These are the primary electrons involved in chemical reactions and bonding. In noble gases, the valence electrons occupy a full outer shell.

• This full occupancy is significant because it minimizes the atom's tendency to participate in chemical reactions.
• For example, neon's eight valence electrons (with an electron configuration of 1s² 2s² 2p⁶) indicate a non-reactive nature, as it's energetically satisfied and doesn’t need to gain or lose electrons.

The concept of valence electrons is vital to understanding the noble gases' role as inert elements; their full valence shell prevents them from engaging in typical chemical behavior and interactions.

Chemical Inactivity

The chemical inactivity of noble gases is an intriguing aspect attributed to their full outer electron shell. This full shell acts like a protective barrier, rendering them inert and rarely reactive under standard conditions.

• The main reason for their inactivity is their complete set of valence electrons; a filled shell doesn't encourage sharing or exchanging electrons with other atoms.
• Although noble gases can engage in chemical reactions under extreme conditions, such as at high pressures or in the presence of powerful catalysts, these occurrences are exceptions rather than the rule.

Their lack of conventional chemical activity illustrates why noble gases are often used in conditions that require non-reactive environments, like in lighting and specialized equipment.