Introduction to Noble Gas
Neon, argon, krypton, and xenon are known as Noble Gas. Those gasses are found in the air and are obtained by liquefying them. Primarily helium is formed from the cryogenic separation of natural gas. Radon is a radioactive Noble Gas. It is produced from the radioactive decay of heavier elements like radium, thorium, and uranium. 118 Elements in the periodic table are manufactured radioactive elements. This radioactive element is produced by striking a target with accelerated particles. Scientists may find some extraterrestrial sources of Noble Gasses shortly. Helium can be more actively found on more giant planets than on Earth.
Introduction to Physical and Chemical Properties of Noble Gasses
In the modern periodic table, group 18 belongs to Noble Gasses. This group consists of a Chemical series of gasses including Argon, helium, neon, krypton, xenon, and radon. Radon is the only radioactive out of all. As the elements of the group hold the maximum number of electrons in their outermost shell, they are considered as the most stable elements of the periodic table. As they are already stable, they react very rarely with the other elements. Noble Gasses are also known as inert and rare gasses. Group 18 was characterized later on as compared to other groups of elements.
During Mendeleev's time, Noble Gasses were not discovered. In the late 18th century, Henry Cavendish was the first person to discover Noble Gasses which were given the place of zero groups and were renamed as group 18 in the periodic table by the IUPAC convention.
Properties of Noble Gas
Those elements belonging to group 18 on the periodic table are Noble Gas. It is located in the column of elements on the right side of the periodic table.
There are seven Noble Gas elements in the periodic table: helium, neon, argon, krypton, xenon, and radon.
Noble Gasses are known as the least reactive Chemical elements. Noble Gasses are nearly inert because their atoms have an entire valence electron shell. So, they have a slight tendency to accept or donate electrons to form Chemical bonds.
Chemical Properties of Noble Gas
There are various Chemical Properties of inert gasses that are mentioned below:
Characteristics of Noble Gases are odorless, non-flammable, colorless, and monoatomic gas with low Chemical reactivity.
All the Noble Gasses conduct electricity and fluorescence which can be needed in many conditions to maintain a constant and safe environment.
All Noble Gasses are insoluble in water.
As they have a complete octet which makes them highly stable. So, they hardly react with other elements to form Chemical bonds because of their less tendency to either gain or lose electrons. But exceptions are everywhere. Xe is the exception in this case. Xenon is the Noble Gas that may form compounds either with fluoride or oxide.
Physical Properties of Noble Gasses
Following are several Physical Properties of inert gasses:
1. Atomic Radii (Atomic size)
As we move down the group from helium to radon the atomic size of Noble Gasses keeps on increasing. This is because when going down the group, the number of occupied shells with valence electrons increases.
2. Boiling and Melting Points
At room temperature and pressure, all the elements of group 18 exist in a gaseous state.
The melting and boiling point of all the Noble Gasses is very low due to the following reasons:
All consist of monatomic molecules that are held together by weak van der Waal forces of attraction.
During melting and boiling of overall Noble Gasses, only a slight amount of heat is required to resist weak interatomic force.
But, As we move down the group, the boiling and melting point of the Noble Gasses increases due to the following reason:
When moving down in the group, the atomic radius increases which results in the formation of a strong Van Der Waals force of attraction between the atoms.
As to overcome the interatomic force of attraction which becomes stronger, it also requires more energy during melting and boiling.
3. Density
All elements of group 18 have low densities. When going down the group, density increases as the atomic mass keeps on increasing.
4. Ionization Energy
In the periodic table, As we move down the group the first ionization energy keeps on decreasing. Noble Gasses have the highest ionization enthalpy from all the groups of the periodic table, reflecting that they are Chemically inert.
5. Ionization Potential
When going down the group, the atomic radii increase which increases the attractive force and ultimately results in the increase of polarity and decrease in the ionization potential. This is because the larger atom of the group in the valence electrons are held together less tightly by the atom as they are situated far away from the nucleus.
6. Electrical and Heat Conductivity
All Noble Gas except neon conducts electricity. All the inert gasses of group 18 are poor conductors of heat.
Spot of the Noble Gasses on the Periodic Table
The Noble Gasses are also known as inert gasses or rare gasses. They are located in Group VIII by the periodic table's International Union of Pure and Applied Chemistry (IUPAC). This column of elements is found on the far right side of the periodic table. This group is a subset of the nonmetals element. The elements are also known as the neon group or the helium group. The Noble Gasses ( with symbol ) are:
Helium (He)
Neon (Ne)
Argon (Ar)
Krypton (Kr)
Xenon (Xe)
Radon (Rn)
All of these elements are gasses at ordinary temperatures and pressure. Radon consists only of radioactive isotopes.
Uses of the Noble Gasses
There are various practical uses of Noble Gasses, those are:
The Noble Gasses are used for inert atmospheres, basically for arc welding.
To protect specimens,
To deter Chemical reactions.
There are neon lamp
Another use is krypton headlamps
Also in lasers.
Helium is used in balloons,
Helium is used in deep-sea diving air tanks,
Also to cool superconducting magnets.
Summary of Noble Gasses
Noble gas is non-reactive. They do not react with any molecule or each other.
At low pressure, Noble gas will conduct electricity and fluoresce.
All the elements have complete electron distribution in the outer shell (oxidation number = 0)
All the element contains High ionization energies
They have Very low electronegativities
They have low boiling points (all monatomic gaseous at room temperature)
No color, odor, or flavor under ordinary conditions (but may form coloured liquids and solids)
Nonflammable
Note: Several properties of the Noble Gasses on the periodic table are positively correlated to the atomic size.The Following Table Shows Some Physical Properties of Inert Gas
FAQs on Noble Gases
1. What are noble gases and which elements belong to this group?
Noble gases are a group of chemical elements that are located in Group 18 of the periodic table. They are known for their extremely low chemical reactivity. The elements classified as noble gases are:
- Helium (He)
- Neon (Ne)
- Argon (Ar)
- Krypton (Kr)
- Xenon (Xe)
- Radon (Rn)
- Oganesson (Og)
Under standard conditions, all these elements exist as odourless, colourless, monatomic gases.
2. Why are the elements of Group 18 called 'noble gases'?
The term 'noble gas' is an analogy to the nobility, who were considered to be above interacting with commoners. Similarly, these elements are called noble because they are highly stable and have a very low tendency to react or form chemical bonds with other elements. This stability is due to their atoms having a completely filled valence electron shell (a full octet, or a duplet in the case of helium), which is the most stable electron configuration an atom can have.
3. What are the key characteristics of noble gases?
The noble gases share several distinct physical and chemical properties as per the CBSE Class 12 curriculum for the 2025-26 session. Key characteristics include:
- State: They are all gaseous at room temperature and pressure.
- Reactivity: They have very low chemical reactivity due to their stable electron configurations.
- Structure: They exist as individual atoms (monatomic) rather than molecules.
- Physical Appearance: They are colourless, odourless, and non-flammable under ordinary conditions.
- Ionisation Enthalpy: They have the highest ionisation enthalpies in their respective periods, making it very difficult to remove an electron.
- Interatomic Forces: They are held together only by weak van der Waals forces of attraction.
4. Where are noble gases located in the periodic table and what is their general electronic configuration?
Noble gases are located in Group 18, which is the rightmost column of the modern periodic table. Their position reflects their status as elements with a full outer electron shell. The general electronic configuration for the valence shell of noble gases is ns²np⁶, where 'n' is the principal quantum number. The only exception is Helium, whose configuration is 1s², as its first and only shell is completely filled with two electrons.
5. What are some important real-world uses of noble gases like helium and argon?
Despite their inert nature, noble gases have several important applications. For example:
- Helium (He) is used in weather balloons and airships because it is lighter than air and non-flammable. It is also used in cryogenic applications and in breathing mixtures for deep-sea divers.
- Neon (Ne) is famously used in glowing advertising signs ('neon signs'), which produce a reddish-orange light when an electric current is passed through the gas.
- Argon (Ar) is used to create an inert atmosphere for arc welding and to protect sensitive materials from reacting with air. It is also used to fill incandescent light bulbs to prevent the filament from deteriorating.
6. Why do noble gases have very low melting and boiling points?
Noble gases have very low melting and boiling points because they exist as single, neutral atoms with no charge. The only forces of attraction between these atoms are the extremely weak van der Waals forces (or London dispersion forces). Since these interatomic forces are so weak, only a very small amount of thermal energy is required to overcome them, allowing the elements to transition from solid to liquid or liquid to gas at very low temperatures.
7. If noble gases are so inert, how is it possible for xenon to form compounds?
While noble gases are generally unreactive, the term 'inert' is not absolute. For heavier noble gases like xenon (Xe) and krypton (Kr), the outermost electrons are further from the nucleus and are shielded by inner electrons. This results in a lower ionisation enthalpy compared to lighter noble gases. Consequently, a highly electronegative element, such as fluorine or oxygen, can attract an electron from xenon and form a chemical bond. This is why compounds like xenon hexafluoride (XeF₆) and xenon trioxide (XeO₃) can be synthesized under specific conditions.
8. How do key physical properties like atomic radii and ionisation enthalpy trend down Group 18?
As you move down Group 18 in the periodic table, there are predictable trends in physical properties:
- Atomic Radii: The atomic radius increases as you go down the group. This is because each subsequent element adds a new principal electron shell, placing the valence electrons further from the nucleus.
- Ionisation Enthalpy: The first ionisation enthalpy decreases as you go down the group. With increasing atomic size and shielding effect from inner electrons, the outermost electron is held less tightly by the nucleus and becomes easier to remove.
9. Why is helium considered a noble gas even though it does not have an octet of 8 valence electrons?
Helium is considered a noble gas because its valence shell is completely filled, which is the defining characteristic of the group. Its electron configuration is 1s². The first electron shell (n=1) can only hold a maximum of two electrons. By having these two electrons, helium achieves a stable configuration known as a duplet. This completely filled shell makes it exceptionally stable and chemically unreactive, just like the other noble gases which achieve stability with a full octet of eight valence electrons.
10. Why were the noble gases discovered much later than other elements?
The noble gases were discovered much later than most other elements primarily due to their chemical inertness. Early chemistry focused on identifying new elements by observing the compounds they formed. Since noble gases rarely form compounds, they escaped detection through traditional chemical analysis. Furthermore, they are present in the atmosphere in very small concentrations and are colourless and odourless, making them difficult to isolate and identify until the development of advanced techniques like fractional distillation of liquid air and spectroscopic analysis in the late 19th century.
