What are Noble Gases?

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The noble gases are group 18 elements of the periodic table. Atoms of these elements have completely filled valence electron shells, making them relatively inert, colourless, odourless, monatomic gases at room temperature and pressure. 

Under the normal conditions of temperature and pressure, all the noble gases exist in the gaseous phase. The term “noble gas” is derived from a translation of the German word Edelgas, which means “noble gas”. 

German chemist Hugo Erdmann termed this phrase in 1898. Like a nobleman consider it undignified to associate with common people, noble gases tend not to react with other elements. Other names for noble gases are rare gases, inert gases, and aerogens. 

The Names of the Noble Gases are:

Noble Gas Properties

They are known to have extremely low chemical reactivity. This is because all the inert gases have stable electronic configurations and they do not form molecules easily and are mostly found as monoatomic gases. The general noble gas configuration is ns2 np6. In this topic we have discussed noble gases definition, Now let’s discuss noble gases properties and the atomic number of noble gases.

Helium (He):

Helium is the first chemical element of group 18 and is denoted by the symbol He. It is the first lightest noble gas and is known to possess the lowest boiling point. It is the second lightest element which is colourless, odourless, and tasteless. The atomic number of helium is 2. It is non-toxic in small concentrations, The electronic configuration of helium is 1s2. So, It has a total of 2 electrons in its valence shell. Helium cannot be solidified by sufficient cooling at normal atmospheric pressure, so it is necessary to apply pressure of 25 atmospheres at a temperature of −272 °C to convert it into a solid form.

This gas constitutes about 23 percent of the mass of the universe and is the second in abundance after hydrogen in the cosmos. Helium is mainly concentrated in stars, where it is synthesized from hydrogen by the nuclear fusion reaction. This gas is used as an inert-gas atmosphere for welding metals such as aluminium and is also used in rocket propulsion.

  • Atomic Number: 2

  • Mass Number: 4

  • Melting point: -272 °C

  • Boiling Point: -268.9 °C

  • Density: 0.178 X 10 -3 g/cm3 at 20 °C

Neon (Ne):

Neon is a second chemical element of group 18 and is denoted by the symbol Ne. The atomic number of neon is 10. Neon exists as a colourless monoatomic gas. This gas does not possess any colour, odour, taste and is lighter than air. The electron configuration of Neon is [He] 2s22p6. It is used commonly in fluorescent lamps and electric signs. This gas occurs in minute quantities in Earth’s atmosphere and is trapped within the rocks of Earth’s crust. This element is more abundant in the cosmos as compared to Earth’s surface. 

  • Atomic Number: 10

  • Mass Number: 20

  • Melting point: -248.4 °C

  • Boiling Point: -246 °C

  • Density: 0.9 g/L

Argon (Ar):

Argon is the third chemical element of group 18 in the periodic table with an atomic number of 18. The element is denoted by the symbol Ar. It is a colourless, odourless, and tasteless gas. The electronic configuration of argon is [Ne]3s23p6. This element has a total of 8 electrons in its valence shell and hence it is non-reactive.

  • Atomic Number: 18

  • Mass Number: 39.948

  • Melting point: -189.4 °C

  • Boiling Point: -185.8 °C

  • Density: 1.784 g/L

Krypton (Kr):

Krypton is the fourth chemical element of group 18 with an atomic number equals to 36. This element is denoted by the symbol Kr. It is about three times heavier compared to air. Krypton is a colourless, odourless, tasteless, and monatomic gas. The electron configuration of krypton is written as [Ar]3d104s24p6.  

  • Atomic Number: 36

  • Mass Number: 83.798

  • Melting point: -157.4 °C

  • Boiling Point: -153.4 °C

  • Density: 1.784 g/L


Xenon is the fifth noble gas with an atomic number of 54. The symbol ‘Xe’ is used to denote xenon.

It is 4.5 times heavier than air, It is a colourless, odourless, and tasteless gas. The term xenon was derived from the Greek word Xenos, meaning “strange” or “foreign.”

  • Atomic Number: 54

  • Mass Number: 131.293

  • Melting point: -157.4 °C

  • Boiling Point: -108.1 °C

  • Density: 5.761 kg/m3


Radon is a sixth noble gas with an atomic number equals 86. It is a heavy radioactive gas generated by the radioactive decay of radium. This is a colourless gas that is 7.5 times heavier compared to air and 100 times heavier than hydrogen.

  • Atomic Number: 86

  • Mass Number: 222.01

  • Melting point: -71 °C

  • Boiling Point: -61.7 °C

  • Density: 9.73 g/litre

Here, we have discussed all the noble gas elements. Let’s have a look at the noble gases periodic table:

[Periodic Table]

FAQ (Frequently Asked Questions)

Q1. How many Noble Gases are there in the Periodic Table?

Answer: There are six noble gases in the periodic table: Helium, Neon, Argon, Krypton, Xenon, Radon.

Q2. Write some Properties of Noble Gases.

Answer: Some properties of Noble gases are listed below:

  • They are nonreactive and are used to form inert atmospheres.

  • They have a complete outer electron or valence shell.

  • They have high ionization energies.

  • Electronegative value is very less.

  • They have low boiling points. (all are monatomic gases at room temperature).

  • They possess no colour, odour, or flavour under ordinary conditions. 

  • They are non flammable.

  • At low pressure, they conduct electricity and fluoresce.

Q3. What is the difference between Octet and Duplet?

Answer: The major difference between the octet and duplet is that an octet is an atom or an ion having a maximum of eight electrons in the outermost shell on the other hand a duplet is an atom having a maximum of two electrons in the outermost shell.