Noble Gases - Trends In Physical And Chemical Properties

The group 18 of the modern periodic table consists of noble gases. Helium, neon, argon, krypton, xenon, and radon are the noble gases. These gases are monoatomic and chemically inert under normal conditions and hence are also named as inert gases. These gases are present in very small quantities in the atmosphere and so they are also called as rare gases. Radon possesses radioactive characteristics. These gases were not discovered at Mendeleev’s time, so he did not specify any place for them in the periodic table. Later on, a new group known as zero group was created to place them in the modern periodic table. According to the IUPAC conventions, group zero has been renamed to group 18.

noble gas

Noble gas

Physical and chemical properties of group 18 elements

The noble gases do not react under normal conditions. The non- reactivity of noble gases is due to the following reasons:

  1. The valence shell of the noble gases is completely filled. The next available shell is of much higher energy.
  2. Noble gases have very high ionization enthalpies.
  3. They have large positive values of electron gain enthalpy.

Noble gases have no tendency to gain or lose electrons under ordinary conditions. This is the only reason due to which they do not participate in chemical reactions and remain inert. According to modern researchers, it has been seen that noble gases can be compelled to take part in a chemical reaction under certain specific conditions.

A scientist named Neil Bartlett found that PtF6 reacts with oxygen and forms O2+ [PtF6]. The ionization energy of oxygen and xenon is comparable, and so PtF6 should react with xenon to form Xe+ [PtF6]. This assumption was proved to be correct and hence he succeeded in isolating the orange-yellow compound, XePtF6. This compound was obtained at room temperature by the interaction of PtF6 with xenon. This discovery of Neil Bartlett led to the further discovery of several other xenon compounds, mainly those formed with the electronegative elements such as fluorine and oxygen. There are only a few compounds of Krypton. Some compounds of radon have been prepared and identified by radiotracer techniques, but their isolation has not been possible. The true chemical nature of compounds of helium, neon, and argon are still unknown.

We have briefly seen the properties of noble gases and the reason for such characteristics. For any further query on this topic, install Byju’s the learning app.

Practise This Question

The noble gases have closed-shell electronic configuration and are monoatomic gases used normal conditions. The low boiling points of the lighter noble gases are due to weak dispersion forces between the atoms and the absence of other interatomic interactions.

The direct reaction of xenon with fluorine leads to a series of compounds with oxidation number +2, +4 and +6. XeF4 reacts violently with water to give XeO3. The compounds of xenon exhibit rich stereochemistry and their geometries can be deduced considering the total number of electron pairs in the valence shell.

XeF4 and XeF6 are expected to be