Which of the following is correct? (1) The hybridization of \(\mathrm{Xe}\) in \(\mathrm{XeF}_{4}\) is \(\mathrm{sp}^{3} \mathrm{~d}^{2}\) (2) Liquid helium is used in cryogenic liquids. (3) \(\mathrm{XeO}_{3}\) has four \(\sigma\) and four \(\pi\) bonds (4) Among the noble gases the occurrence of argon is highest in air (a) \(1,2,4\) (b) \(2,3,4\) (c) \(1,3,4\) (d) \(1,2,4\)

Understanding hybridization in molecules is crucial when studying chemistry, especially when predicting the shape of molecules and their chemical properties. Hybridization is a model that describes the reshuffling of the valence electrons of an atom to make it more suitable for bond formation with other atoms.

In the case of the molecule XeF₄, xenon undergoes sp³d² hybridization. This concept explains how xenon, which normally has valence orbitals in separate energy levels, can promote some of its electrons and then hybridize to form a total of six equivalent sp³d² hybrid orbitals. Four of these orbitals form sigma bonds with fluorine atoms, and the remaining two accommodate lone pairs of electrons, resulting in a square planar geometry as predicted by the VSEPR theory.

Cryogenic liquids play a pivotal role in diverse fields due to their capability to achieve extremely low temperatures. One primary application is in the field of superconductivity, where materials can conduct electricity with zero resistance when cooled to cryogenic temperatures.

Liquid helium, which has a boiling point of just 4.2 K, is essential in reaching such low temperatures. It's used to cool the superconducting magnets in MRI machines and particle accelerators. Moreover, in space exploration, cryogenic liquids are used to store and transport large quantities of fuel in a compact form. In addition, they serve an important role in cryopreservation methods in biological research and medicine for the preservation of cells, tissues, and even whole organs.

The Valence Shell Electron Pair Repulsion (VSEPR) theory offers valuable insights into molecular geometry and structure. It is based on the idea that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion.

For instance, in xenon trioxide (XeO₃), VSEPR theory predicts a trigonal planar geometry. Each oxygen forms a double bond with xenon, consisting of one sigma (\f\((\f\)\right) and one pi (\f\(pi\f\)) bond. The bond angles are approximately 120 degrees, reflecting the three regions of electron density around xenon - all of which are bonding pairs. This directly correlates to the incorrect option in the exercise stating that XeO₃ has four sigma and four pi bonds.

The noble gases, known for their low reactivity, are a group of chemical elements that include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn). Among them, argon is the most abundant in the Earth's atmosphere.

Argon composes approximately 0.934% of the atmosphere by volume, predominantly resulting from the decay of potassium-40 in the Earth's crust. This abundance makes argon readily available for various industrial uses, such as providing an inert gas shield for arc welding, in incandescent light bulbs to protect the filament from oxidation, and in the preservation of historical documents and materials.