Full outer shell
Why noble gases hardly react.
Quiet gases
Helium, neon and argon are noble gases. They show little chemical activity.
What do their atoms have in common that explains this?
What this lesson covers
The idea
Noble gases, which have a completely filled valence shell, are chemically very unreactive; the reactivity of other elements is explained as a tendency to attain a completely filled valence shell.
Quiet gases
Helium, neon and argon are noble gases. They show little chemical activity.
What do their atoms have in common that explains this?
- A completely filled outermost shell
- Only one electron each
- No electrons at all
Count the electrons
Open every tab. Dots on the rings are electrons in the shells K, L, M.
Why atoms react
Noble gases such as helium, neon and argon have a completely filled valence shell, and they show little chemical activity. Other elements do not have a filled valence shell. We explain their reactivity as a tendency to attain a completely filled valence shell.
Noble gases, which have a completely filled valence shell, are chemically very unreactive; the reactivity of other elements is explained as a tendency to attain a completely filled valence shell.
Notes
Noble gases have a completely filled valence shell and are unreactive; other elements tend to attain a filled valence shell.
Check yourself
Noble gases show little chemical activity because they have ...
Which of these has a completely filled valence shell?
The reactivity of other elements is explained as a tendency to ...
Argon has 2, 8 and 8 electrons in its shells. How many electrons does an argon atom have in all?
Answer: 18
2 + 8 + 8 = 18, which is argon's atomic number.
- a single outer electron. A single outer electron is how sodium is arranged (2, 8, 1), and sodium is reactive.
- a completely filled valence shell — correct. Yes!
- no valence shell. Noble gases have a valence shell, and it is completely filled.
- Sodium (2, 8, 1). Sodium has one electron in its outermost shell.
- Chlorine (2, 8, 7). Chlorine has seven electrons in its outermost shell and needs one more.
- Neon (2, 8) — correct. Yes!
- attain a completely filled valence shell — correct. Yes!
- lose all their protons. The explanation in the book is about electrons and the valence shell, not protons.
- stay exactly as they are. Elements react as they tend to attain a completely filled valence shell.