Why Noble Gases Are Chemically Inert
Noble gases (Group 18: He, Ne, Ar, Kr, Xe, Rn, Og) are called inert gases because they rarely form compounds. The reasons are:
1. Stable Electron Configuration
- Their outermost shell (valence shell) is completely filled.
- He → 1s²
- Ne → 2s²2p⁶ (full octet)
- Since the octet (or duet in helium) is stable, they have no tendency to gain, lose, or share electrons.
2. High Ionization Energy
- Removing an electron from a noble gas requires a very large amount of energy because of stable configuration.
- This makes them resistant to forming cations.
3. Zero or Very Low Electron Affinity
- They don’t accept extra electrons easily because their shells are already full.
- Thus, formation of anions is not favorable.
4. High Stability of Atomic State
- Noble gases exist as monoatomic gases (single atoms, not molecules).
- They are already in the most stable form, so they don’t combine with other atoms under normal conditions.
5. Low Polarizability
- Their electron clouds are tightly bound and difficult to distort.
- This reduces attractive interactions with other atoms or ions.
Exceptions – When Noble Gases React
- He, Ne, and Ar are almost completely inert.
- But heavier noble gases (Kr, Xe, Rn) can form compounds with highly electronegative elements like fluorine and oxygen, under special conditions.
- Examples: XeF₂, XeF₄, XeF₆, XeO₃.
- Reason: Larger atoms (like Xe) have lower ionization energy and can be polarized more easily.
In short: Noble gases are chemically inert because of their full valence shells, high ionization energy, very low electron affinity, and stable atomic state.