CHEM2077: Chemistry of the Elements - Lecture 9 (Noble Gases)

Vocabulary flashcards covering the physical properties, uses, chemistry, and bonding models of Group 18 Noble Gases based on CHEM2077 Lecture 9.

Noble Gas Electronic Configuration

A stable $ns^2 np^6$ valence configuration, with the exception of Helium which is $1s^2$.

Monoatomic gases

The physical state in which all noble gases exist at room temperature.

Helium (He)

Used in liquid form at $4\,K$ as a coolant in NMR spectrometers.

Argon (Ar)

A noble gas commonly used to provide an inert atmosphere for chemical reactions.

Neon and Krypton

Noble gases used in lighting where excited gas atoms emit light upon relaxation.

Xenon (Xe)

The noble gas that displays the most extensive covalent chemistry due to its relatively low ionization energy.

$$XeF_2$$

A xenon fluoride formed in sunlight with a linear structure and VSEPR classification $AX_2E_3$.

$$XeF_4$$

A xenon fluoride formed at higher temperatures and pressures with a square planar structure and VSEPR classification $AX_4E_2$.

$$XeF_6$$

Formed with excess fluorine and high pressure, it has a "distorted octahedron" structure ($AX_6E_1$) due to a stereochemically active lone pair.

$$XeO_3$$

A powerful and dangerous explosive in the +6 oxidation state formed by the hydrolysis of $XeF_4$ or $XeF_6$.

$$XeO_4$$

A volatile and unstable noble gas oxide in the +8 oxidation state.

Perxenate ($XeO_6^{4-}$)

An extremely powerful oxidizing agent containing Xenon.

Hypervalency (VBT)

Explained in Valence Bond Theory through hybridization involving d-orbitals, such as $sp^3d$ for $XeF_2$ and $sp^3d^2$ for $XeF_4$.

3-centre 4-electron (3c-4e) bond model

A Molecular Orbital (MO) theory model that explains bonding in species like $XeF_2$ using only p-orbitals without requiring high-energy d-orbitals.

3c-4e electron distribution

Four electrons occupy one bonding MO, one non-bonding MO (centered on the Fluorine atoms), and one empty anti-bonding MO.

Noble Gas Reactivity

The highest oxidation states (+6 and +8) are only stabilized by the most electronegative elements, Fluorine and Oxygen; compounds are typically powerful fluorinating or oxidizing agents.