Helium, Neon, Argon, Krypton, Xenon, and Radon (collectively known as the noble gases) possess a zero valency.
The reason these elements exhibit zero valency stems from their electron configuration. Valency refers to the combining capacity of an element, which is determined by the number of electrons an atom needs to gain, lose, or share to achieve a stable electron configuration, typically a full outer electron shell (octet rule).
Why Noble Gases Have Zero Valency
- Complete Outer Shell: Noble gases have a full outermost electron shell. Helium has 2 electrons in its single shell (which is a stable configuration), while the others have 8 electrons in their outermost shell.
- Chemical Inertness: This complete electron shell makes them exceptionally stable and unreactive. They don't readily form chemical bonds with other atoms.
- Zero Requirement for Electron Transfer: Because their outer shells are already full, they have no tendency to gain, lose, or share electrons. Therefore, their combining capacity (valency) is zero.
Examples
| Element | Symbol | Electron Configuration | Valency |
|---|---|---|---|
| Helium | He | 1s2 | 0 |
| Neon | Ne | [He] 2s2 2p6 | 0 |
| Argon | Ar | [Ne] 3s2 3p6 | 0 |
| Krypton | Kr | [Ar] 4s2 3d10 4p6 | 0 |
| Xenon | Xe | [Kr] 5s2 4d10 5p6 | 0 |
| Radon | Rn | [Xe] 6s2 4f14 5d10 6p6 | 0 |
These elements are sometimes referred to as inert gases because of their general lack of chemical reactivity. However, some noble gases, particularly Xenon and Krypton, can form compounds with highly electronegative elements like fluorine and oxygen under specific conditions. But under normal circumstances, they display zero valency.
