Why do 8 electrons form a stable shell? Why not 7? 6? 4? 2?
It isn't quite as simple as that, and some heavier elements have more than 8 in their outer shell, but 8 is very common and I'll try to explain why. Electrons are organized into shapes called Orbitals. 2 electrons can share an orbital, each with opposite spin.
The Short Answer
It isn't quite as simple as that, and some heavier elements have more than 8 in their outer shell, but 8 is very common and I'll try to explain why. Electrons are organized into shapes called Orbitals. 2 electrons can share an orbital, each with opposite spin. The simplest orbital shape is a sphere (S orbital), so the first orbitals that fill are the spherical ones, and 2 electrons go there. The next simplest orbital shape is kinda like a figure 8 (P orbital). Imagine 2 balloons tied together by their opening/valve/pointy end. Since a figure 8 doesn't fill space fully, more than one can fit overlapping. In fact you get a figure 8 aligned with the x axis, the y axis, and the z axis. Together the shape looks just like the shape that happens if you tie 6 balloons together at the pointy end. That's 3 more orbitals, 2 electrons each for another 6 electrons in the P orbital. Once electrons fill these 8 places, they start over again filling a bigger sphere.
Analysis
Key Concepts: Electrons, orbital, shape
This explanation focuses on electrons, orbital, shape and spans 164 words across 11 sentences. At 128% above the average Science explanation (72 words), this is one of the more thorough answers in this category, reflecting the complexity of the underlying question.
What This Answer Covers
The explanation opens with: “It isn't quite as simple as that, and some heavier elements have more than 8 in their outer shell, but 8 is very common “ It then elaborates by presenting a contrasting perspective, ultimately building toward a complete picture across 11 connected points.
How This Compares in Science
Ranked #16 of 500 Science questions by answer depth (top 4%). This places it in the comprehensive tier — the top quarter of most thoroughly answered questions. Questions at this depth typically involve multi-faceted topics requiring nuanced explanation.
Frequently Asked Questions
Is there a simple explanation for why 8 electrons form a stable shell? why not 7? 6? 4? 2?
It isn't quite as simple as that, and some heavier elements have more than 8 in their outer shell, but 8 is very common and I'll try to explain why. Electrons are organized into shapes called Orbitals. 2 electrons can share an orbital, each with…
How detailed is this explanation compared to similar Science questions?
This is one of the most thorough answer at 164 words, ranked #16 of 500 Science questions by depth. The key concepts covered are electrons, orbital, shape.
What approach does this answer take to explain 8 electrons form a stable shell? why not 7? 6? 4? 2?
The explanation uses contrasting perspectives across 164 words. It is categorized under Science and addresses the question through 1 analytical lens.