Noble Gas

The modern periodic table consists of seven periods and eighteen groups. The reason behind the dividing the periodic table into groups and period is to make the study of elements and compounds easier. The modern periodic table is the period function of atomic number. The chemical and physical properties repeat itself when moving across the period and group. The noble gas (group 18) elements have the Outermost configuration of  ns2, np6. Therefore, they have a little or no tendency to react with other elements to form compounds.

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 Noble Gas Definition

It defined as the group 18 elements which are chemically inert and have little tendency to undergo any reaction, hence these were referred to as inert gases, zero-valent gases or zero group elements.

  • These gases have a highly stable configuration.
  •  However, researchers have shown that under certain specific conditions these gases react with certain elements to form compounds. Therefore, nowadays, these gases are more correctly called as noble gases rather than inert gases; the word ‘noble’ signifies that they undergo very few chemical reactions.

Noble Gases on Periodic Table

The zero group of the periodic table consists of six gaseous elements namely helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). Except for radon all of them are present in very small amounts in the atmosphere (hence their name rare gases). Radon is produced by the disintegration of radium and is radioactive itself.

Mendeleeff did not provide any blank space for the noble gases in his periodic table although he provided such spaces for several other elements not known at that time. He could not imagine the existence of elements that avoid participating in chemical reactivity under ordinary conditions. However, Ramsay, the discoverer of these gases, introduced a new group in the periodic table. He classed them as a separate group of “no valency’ or ‘zero valency’ and hence called it as zero group.

Noble Gas

Characteristics of Noble Gases

  1. Atomic Radii. Their atomic radii increase with the increase in atomic number because at each successive step new shell is being added.
  2. Ionization energies. Since their outermost orbits have the stable configuration, they possess very high ionization energies. The ionization energy of the noble gas is highest among the members of the same period. However, their ionization energies decrease on moving down the group because of the increase in atomic radii (size effect) and screening effect.
  3. Electron affinity. Due to complete octet, gas atoms are unable to take extra electron hence their electron affinities are almost zero.
  4. Monoatomicity. Due to very high ionization energies and nearly zero electron affinity, gas atoms are not capable of combining even amongst themselves and hence they exist as single atoms.
  5. Forces of attraction between atoms of noble gases. The noble gases are monoatomic but the fact that these can be liquefied indicates the presence of some forces of attraction between the atoms. But since the noble gases have stable octet in their valence shell, the attractive force between gas atoms must be weak i.e. van der Waals type.
  6. Liquefaction. Since only the very weak van der Waal’s forces of attraction exist in these gases, these are relatively difficult to be liquefied. Further, as the van der Waals forces increase from He to Xe, the ease of liquefaction of these gases increases with the increase in their atomic weights.
  7. Solubility in water. These gases are only slightly soluble in water. However, solubility in water.
  8. Chemical nature. Noble gases are almost chemically inert. However, Kr, Xe and Rn have been found to react chemically; the reactivity increases from Kr to Rn. However, the reactivity of radon has not been studied much because of the radioactive nature of the gas.

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Noble Gas Notation

While writing the notation make sure that you have written with the nearest inert gas element.

Element Configuration Nearest Noble Gas Notation
Na (Sodium) 1s2,2s2,2p6,3s1 [Ne]=1s2,2s2,2p6 [Ne]10,3s1
Mg (Magnesium) 1s2,2s2,2p6,3s2 [Ne]=1s2,2s2,2p6 [Ne]10,3s2
 Al (Aluminum)  1s2,2s2,2p6,3s2,3p1  [Ne]=1s2,2s2,2p6  [Ne]10,3s2,3p1
 K (Potassium)  1s2,2s2,2p6,3s2,3p6,4s1  [Ar]=1s2,2s2,2p6,3s2,3p6  [Ar]18,4s1

 Noble Gas Uses

Noble gases are widely used to provide an inert atmosphere in welding and cutting (antioxidant), in electric bulbs (prolongs filament life), etc. They are also used as coolants for low-temperature work. Amongst the noble gases only helium and argon are easily available and hence these are most widely used.

  • Neon tubes are used in various fields of electrotechnology for rectifiers, voltage, regulators, inductors, etc.
  • Neon lamps are used in botanical gardens and in the greenhouses as it stimulates growth and is effective in the formation of chlorophyll.
  • The chief use of argon is in filling incandescent lamps where it has following advantages over nitrogen.
  • The most important use of argon is in welding and other operations which require a non-oxidising atmosphere and absence of nitrogen.
  • Xenon is used in discharge tubes for producing a high-speed flash of bluish light which is used in quick photography. The flash sometimes lasts for 1/500,000th part of a second.
  • The xenon lamp is used as a source of light.
  • Radon, being extremely radioactive, even more than radium, is used in the treatment of cancer (radiotherapy).

Noble Gas Electron Configuration

Atomic Number  Element Electronic Configuration
2 Helium 1s2
10 Neon [He] 2s2p6
18 Argon [Ne]3s23p6
36 Krypton [Ar]3d104s24p6
54 Xenon [Kr]4d105s25p6
86 Randon [Xe]4f145d106s26p6

From the above table it is obvious that all of them, except helium, have the highly stable s2p(octet) configuration in the outer (valence) shell. Helium has the stable s2 (duplet) configuration. Because of this configuration, they are chemically unreactive and possess zero valencies.

Heaviest Noble Gas

Randon is one of the heaviest among noble gases. Its atomic number is 86. The total 86 electrons complete the outermost octet so as to achieve the maximum stability.

Lightest Noble Gas

Helium is the lightest among noble gases. Most helium was formed during the Big Bang.  It is the second lightest element in the periodic table. Its configuration is 1s2

Radioactive Noble Gas

Radon is a chemical radioactive element with symbol Rn. It is a radioactive, colorless, odorless, tasteless gas. It is obtained when radium disintegrate.

Noble Gas Colors

Element Colors
Helium Pale yellow to orange
Neon Reddish-orange
Argon Purple to pale lavender blue
Krypton Lime green
Xenon  light blue
Radon Deep red

Is Helium a Noble Gas?

Helium is the first element in the gas group. Its boiling point is the lowest among all the elements. Its outermost shell is complete. So, It achieved having oxidation number zero.

Is Hydrogen a Noble Gas?

The answer is No. Its position is still not fixed in a periodic table. It is not a inert gas because its outermost shell is not fully filled (1s1).

Is Argon a Noble Gas?

Yes, it is a noble gas. Due to its inert property, it is used in electric bulbs so that to escape the reaction inside it.

Is Neon a Noble Gas?

Yes, it’s a noble is placed in group number 18 below helium. it’s used in lighting the colourful hoarding boards.

Is Oxygen a Noble Gas?

No, It belongs to group 17 (halogen group).

Is Nitrogen a Noble Gas?

Nitrogen is not an inert gas. The electronic configuration is [He] 2s2p3. Third group: group VA called as Nitrogen group.

Is Chlorine a Noble Gas?

Fifth group: group VIIA called as Halogens. Chlorine is not a noble gas.

Is Krypton a Noble Gas?

Krypton used with other rare gases in fluorescent lamps. Yes, it is a noble gas element.

Noble Gas Properties

  •  The property of noble gases to react chemically involves the loss of electrons, hence the highly electronegative element (F and O) can combine with these gases very easily.
  • Xenon, having the least I.E., forms the largest number of compounds than any other gas.
  •  Krypton forms some compounds but with difficulty as compared to xenon.
  • The lighter members (He, Ne and Ar) are not found to form any compound. Thus the important gas compounds include fluorides and oxides of xenon.
  • Among the three known fluorides (XeF2, XeF4 and XeF6), xenon tetrafluoride is the most important; while among oxides, xenon trioxide is more important than the tetroxide.
  • Xenon tetrafluoride was the first xenon fluoride to be prepared by Classen, Selig, and Malm in 1962.