Wednesday, 7 January 2015

4.2 Group 18 Elements

Physical properties
■ Elements of Group 18

Helium, He
Neon, Ne
Argon, Ar
Kripton Kr
Xenon, Xe
Radon, Rn

The following mnemonic method can be used to memorize the sequence of elements in Group 18.
Henry Never Arrived; Karen eXited with Ron
■ Physical properties

Atomic size of the elements increases as it goes down the group because an additional shell is added to each element.

Solubility, heat and electricity conductivity: Cannot dissolve in water and cannot conduct electricity and heat.

Melting and boiling point
Under room conditions, they are colourless gases with low melting and boiling point.
Very little heat is required to overcome the weak van der Waal’s forces present between the atoms of the gases.

Low density because the atoms are very far apart.

The animation below shows the changes in physical properties of Group 18 elements down the group.
■ This video contains information on the properties of Group 18 in the Periodic Table.

Stability of noble gas
■ Arrangement of electron in noble gases.

Element Electron configuration Arrangement of electron
Helium 2
Neon 2.8
Argon 2.8.8
Duplet electron arrangement or octet electron arrangement are very stable as the outermost shell is filled with the maximum number of electrons.
■ Stability of noble gas

Chemically in-reactive(inert).

Exist as mono-atomic gases which cannot combine ionically or covalently with any other element.

Brief explanation on the stability of noble gases.
Noble gases have the maximum number of valence electrons on the outermost shell, which is two or eight valence electrons.
Their outermost shells are completely filled which are a stable electron arrangement.
As their valence shells are complete, these atoms cannot accept, donate or share electrons with other elements.
Thus they are chemically not reactive or also known as inert.

Uses of inert gas
○ Hot air balloons.
○ Mixed with oxygen and used by divers.
Neon: Advertising light bulbs and airplane landing light.
Xenon: An anaesthetic in the medical field.
Argon: Electric bulbs.
Krypton: Flash lamps in photography.
Radon: To treat cancer patients.

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