6.14 - Why noble gases are chemically inert
Noble gases are much less reactive than most other elements. This lesson connects their electronic configurations to this low reactivity, including why helium is stable with only two electrons.
A full outer shell
The noble gases occupy Group 0 of the periodic table (also called Group 18). They are chemically inert, meaning very unreactive under ordinary conditions. The reason lies in their electronic configurations: the arrangements of electrons in shells around their nuclei.
| Noble gas | Electronic configuration | Outer shell |
|---|---|---|
| helium | 2 | full first shell: 2 electrons |
| neon | 2.8 | full outer shell: 8 electrons |
| argon | 2.8.8 | stable outer shell: 8 electrons |
Helium does not need eight electrons. Its only shell is the first shell, which is full with two. A full outer shell is a stable electronic arrangement. The shared feature of these atoms is a full outer shell, not an identical total number of electrons.
[DIAGRAM: asset_name: noble_gas_full_outer_shells: Noble gas full outer shells compared with reactive atoms - diagram 1; asset_slug: 160_6_14_noble_gases_are_chemically_inert_compared_with_the_other_elements_in_terms_diagram1; file: 160_6_14_noble_gases_are_chemically_inert_compared_with_the_other_elements_in_terms_diagram1.png; recommended_method: deterministic_drawn; description: Exact monochrome electron-shell comparison for Pearson Edexcel 1CH0 6.14. The left side shows helium 2, neon 2.8 and argon 2.8.8 with full outer shells labelled. The right side contrasts sodium 2.8.1 and chlorine 2.8.7 as examples of other elements with outer shells that are not full. The teaching point is that noble gases are chemically inert because their electronic configurations already have full outer shells, whereas many other elements react to gain, lose or share electrons. Deterministic drawing is required because electron counts and labels are assessed content.]
Continue this lesson.
You’re previewing NovaLearn without an account. Create a free account to read the rest.
Create free account