CIE iGCSE Co-ordinated Sciences-C8.5 Noble gases- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-C8.5 Noble gases – Study Notes
CIE iGCSE Co-ordinated Sciences-C8.5 Noble gases – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Describe the Group VIII noble gases as unreactive, monatomic gases and explain this in terms of electronic configuration
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Group VIII Noble Gases
Group VIII elements, commonly known as noble gases, include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). They occupy the far-right column of the Periodic Table and are characterised by their exceptional stability and lack of chemical reactivity.
Key Properties:
Electronic configuration and unreactivity:
Noble gases have complete outer electron shells, which gives them a stable electronic configuration. Helium has 2 electrons (1s²), while the others have 8 electrons in their outer shell (ns² np⁶). Because their valence shells are full, they have no tendency to gain, lose, or share electrons, making them extremely unreactive or inert under normal conditions.
Monatomic nature:
Each noble gas exists as a single atom (monatomic) rather than forming molecules. There is little or no attraction between atoms, except weak van der Waals forces, which means they exist as separate atoms at room temperature and pressure.
Other physical properties:
Noble gases are colourless, tasteless, and odourless gases under standard conditions. They have low boiling and melting points due to weak interatomic forces. They are also non-flammable and poor conductors of electricity in their neutral state.
Explanation of Unreactivity:
The chemical behaviour of elements is largely determined by the number of electrons in their outermost shell. Noble gases have completely filled outer shells, which correspond to the stable electronic arrangements similar to the inert group of helium or the octet rule for other noble gases. As a result:
- They do not form bonds readily.
- They do not react with metals or non-metals under standard conditions.
- Exceptions exist only under extreme conditions (e.g., xenon can form compounds with fluorine or oxygen under high pressure or in the presence of catalysts).
Example
Explain why argon is chemically inert.
▶️Answer/Explanation
Argon has the electronic configuration \( 1s^2 2s^2 2p^6 3s^2 3p^6 \), giving it a full outer shell of 8 electrons. Because it already has a stable octet, argon does not need to gain, lose, or share electrons. Therefore, it is chemically unreactive under normal conditions.
Example
Why are helium atoms monatomic at room temperature?
▶️Answer/Explanation
Helium atoms have a full outer shell (1s²) and do not need to form bonds. As a result, helium exists as individual atoms rather than molecules at room temperature. Weak van der Waals forces between helium atoms are insufficient to form molecular structures, so helium remains monatomic.
Example
Describe why xenon can sometimes form compounds even though it is a noble gas.
▶️Answer/Explanation
Xenon has a full outer shell but is a larger atom with lower ionisation energy than lighter noble gases. Under extreme conditions, such as high pressure, high temperature, or in the presence of strong oxidising agents like fluorine or oxygen, xenon can be forced to share electrons and form compounds (e.g., XeF₂, XeO₃).