The Periodic Table of Elements - Elements in Group 18
The Periodic Table of Elements
Group 18 Elements
Group 18 is also referred to as group 0 depending on which syllabus you are learning. In the SPM KSSM syllabus, it is referred to as Group 18. However, in the IGCSE syllabus, it is referred to as Group 0. For the sake of simplicity, I will be referring to it as Group 18 for the rest of the post.
The elements in Group 18 are helium, neon, argon, krypton, xenon, radon and oganesson. Oganesson, Og will not be discussed in this post.
Group 18 elements:
- exist as gases
- are monoatomic – made up of one atom only
- are very unreactive/inert (this is why they are called noble gases)
Group 18 is located at the right end of the periodic table. (refer to the periodic table above)
Uses of Group 18 Elements
Group 18 elements are found naturally existing in the atmosphere. They have various uses as in the table below:
| Group 18 Element | Use | Explanation |
|---|---|---|
|
Helium |
Hot air balloons and air ships |
Much lighter than air and non-flammable |
|
Neon |
Advertising lights |
Glows red when current is passed through it. Other colours can be formed by mixing gases. |
|
Argon |
To provide an inert environment |
Incandescent light bulbs (tungsten filament light bulbs) are filled with argon because argon does not react with tungsten at high temperatures. Air containing oxygen would react with tungsten and cause the tungsten filament to form an oxide and burn away.
Argon gas is introduced into welding sites to prevent metals from reacting with oxygen. Again, this is because it is inert (unreactive). |
|
Krypton |
Camera flashlights and lasers in eye surgery |
It produces a brilliant white light. |
|
Xenon |
Lighthouse lamps, car headlamps, operating theaters |
It produces a bright light with a blue tinge - mimicking daylight. |
Physical Properties of Group 18 Elements
- Atomic radius increases down the group. This is due to an increase in the number of electron shells down the group.
- Density increases down the group. As the atomic mass increases, the density increases. (density = mass/volume)
- Atoms of noble gases are held together by weak van der Waals forces of attraction. The strength of the forces of attraction increases down the group. As a result, more heat energy is required to break the bonds between atoms. Therefore, the melting and boiling points of the elements increase down the group.
- As non-metals, noble gases are not capable of conducting electricity.
- They are insoluble in water
Chemical Properties of Group 18 Elements
Group 18 elements are very unreactive or inert. As mentioned earlier in the post, this is why they are called noble gases.
So, why do they refuse to react with other elements?
Two things – duplet electron arrangement and octet electron arrangement. Both are stable electron arrangements in the outermost shell.
Chemical reactions involve either gain, loss or sharing of electrons. The purpose of this is to achieve a stable electron arrangement. Since noble gases have already achieved a stable electron arrangement, they do not need to transfer or share electrons. Therefore, they are unreactive.
- A duplet electron arrangement consists of a full outer shell of electrons with only two electrons.
- This is only possible for the first shell.
- There is only one neutral element that fits the brief – helium! (refer to diagram)
- An octet electron arrangement consists of a full outer shell of electrons with 8 electrons.
- Other than helium, the other noble gases have an octet electron arrangement. (refer to diagram)
Practice Questions
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