Group 18 Elements Noble Gases
As a kid, we all love to buy balloons that float in the air, seeing the balloon floating in the air without any fans and engines always makes us feel like its a magic. Well, indeed its a magic but, its a magic of science. We still personally know how it feels when the balloon you just bought flys away as you were lost in eating ice-cream in the fair.
That feeling is terrible, so to save your balloon we tell you a little trick, always tie the thread of your ballon with your one hand, the one you don’t use, don’t tie it on your fingers, tie it on one of your arms and have a great time. Well, nostalgia’s apart let us discuss what indeed makes a balloon fly away on its own. Today we are going to talk about group 18 elements, there occurrence in nature, properties, and some interesting facts to amaze you.
Group 18 Periodic Table
The group 18 elements are called noble gases, and all of the 18 group elements are colorless, odorless, tasteless, and non-flammable gases under normal conditions and room temperature.
The elements of group 18 are Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Re).
All of these elements from group 18 of the periodic table occur naturally on earth. Any given element is said to be noble gas if it doesn’t react with other chemicals and is inert to them. It has been discovered that elements from group 18 cannot form bonds with other atoms and thus are not able to form any compound. But later as the technology gets better and scientists were able to find the electronic structure it was found even noble gases can form some compounds.
Also, when they were first discovered, scientists said these elements are quite rare. Now in the 21st century, we know they are well abundant elements on earth and in-universe, so saying them as a rare element is an entirely false statement.
When we are referring something as noble in terms of chemistry, it means that the following element will show reluctance to metals. Some of these elements are gold and platinum. The same property is applicable for elements from 18 groups of the periodic table.
Why Are Elements of Group 18 Inert In Nature?
Group 18 elements are called inert due to their atomic structure which gives them little tendency to perform any chemical reactions. The outer shell of these elements is considered to be full, leaving no space for the share or transfer of electrons from another element.
Image will be uploaded soon
The atomicity of noble gases is one meaning each individual molecule has one element of a given noble gas. In normal conditions, these gases are present in monoatomic. As a result, the atomicity is 1. Helium is one of the best examples that shows theses nobles gases have one atomicity. All the elements present in group 18 either have duplets or octets in their valance shell. As a result, they don’t have any inclination to form compounds by reacting with other elements. It shows inert behavior to other chemicals.
Furthermore, their valency is zero, so they don’t take any electron, and neither do they impart any electron from their valance shell. As a result, they are inert.
Properties of Elements From 18 Group
You would be shocked to know some of these facts and properties but the one gas that gives a ballon ability to fly without any engine is the most abundant rare gas in the atmosphere. Yes, helium is 0.000052% of the total air present in our earth’s atmosphere. Just like that, we have written down some important properties for group 18 elements.
On the other hand, if speaking about the earth as a whole the most abundant noble gas is Argon due to its stable nucleus giving the element inert properties.
The nuclear radius gets an increment as we move down the group 18 due as we witness the increase in nuclear number. As we move from top to the bottom of the group, each progressive element will have show the expansion by adding up new shells.
The elements have high ionization potential due to their closed electronic configuration.
In addition to this, the particles hold each other with weak Vander Walls Force. As we go down and the new shells get added to each element, the extent of these forces increases along with the polarizability of molecules.
Due to weak Vander Wall forces, these elements have lower boiling and melting points.
As we go down the liquefaction of these gases becomes easier as the new shell is added after each element, leading to an increase in the Vander wall forces.
FAQs on Occurrence of Group 18 Elements
1. What are the Group 18 elements, and which elements belong to this group?
The Group 18 elements in the periodic table are a family of chemically inert gases known as the noble gases. They are characterised by their completely filled valence electron shells, which makes them highly stable. The elements in this group are:
- Helium (He)
- Neon (Ne)
- Argon (Ar)
- Krypton (Kr)
- Xenon (Xe)
- Radon (Rn)
2. What is the general occurrence of Group 18 elements in nature?
All noble gases, except for Radon, occur in the Earth's atmosphere. Their atmospheric abundance by volume is about 1%, with Argon being the major constituent. Helium and sometimes Neon are also found in minerals of radioactive origin (e.g., pitchblende, monazite) and in natural gas. Radon is a product of the radioactive decay of Radium-226 and is found in trace amounts near radioactive mineral deposits.
3. Which noble gas is the most abundant in the atmosphere, and how does this compare to its abundance in the universe?
The most abundant noble gas in the Earth's atmosphere is Argon (Ar), making up about 0.934% of the air by volume. However, in the universe, Helium (He) is the most abundant noble gas and the second most abundant element overall, after Hydrogen. This highlights the difference between terrestrial and cosmic abundance.
4. Why are the elements of Group 18 known as 'noble gases' or 'inert gases'?
They are called 'noble gases' because of their extremely low chemical reactivity, a property historically associated with the 'nobility' of metals like gold and platinum that resist change. This inertness is due to their stable electron configuration, with a completely filled outermost shell (a duplet for Helium, and an octet for the others). This stability means they have very little tendency to gain, lose, or share electrons to form chemical bonds under normal conditions.
5. What are the key periodic trends observed in Group 18 elements as you move down the group?
As you move down Group 18 from Helium to Radon, several trends are observed:
- Atomic Radius: The atomic radius increases due to the addition of a new electron shell with each successive element.
- Ionisation Enthalpy: The energy required to remove an electron decreases. This is because the outermost electron is further from the nucleus and is better shielded by inner electrons, making it easier to remove.
- Boiling Point: The boiling point increases down the group. This is due to the strengthening of the weak van der Waals forces of attraction as the size and mass of the atoms increase.
6. Why do noble gases have very low melting and boiling points?
Noble gases exist as individual, monoatomic particles. The only intermolecular forces holding these atoms together in a liquid or solid state are very weak instantaneous dipole-induced dipole attractions, also known as London dispersion forces or van der Waals forces. Since these forces are extremely weak, very little thermal energy is required to overcome them, resulting in very low melting and boiling points.
7. If noble gases have a stable electron configuration, how is it possible for some of them to form compounds?
While it was once believed that noble gases were completely inert, it was discovered that the larger noble gases, specifically Xenon (Xe) and Krypton (Kr), can form compounds. This is possible because as you go down the group, the ionisation enthalpy decreases significantly. For Xe and Kr, the outermost electrons are far enough from the nucleus that they can be shared with highly electronegative elements like fluorine and oxygen to form compounds such as XeF₂, XeF₄, and XeO₃.
8. What are some important examples of the real-world applications of noble gases?
The unique properties of noble gases make them useful in various applications:
- Helium (He): Used in weather balloons, airships, and as a cryogenic agent for cooling superconducting magnets in MRI scanners.
- Neon (Ne): Famously used in brightly coloured advertising signs ('neon lights') and television tubes.
- Argon (Ar): Provides an inert atmosphere for welding and in incandescent light bulbs to prevent the filament from burning out.
- Krypton (Kr) & Xenon (Xe): Used in high-intensity lamps, lasers, and photographic flashes due to their ability to produce bright white light.
