Six elements that almost never react — tap a tube to see it light up the way it really does in a discharge lamp, and learn what makes it unique.
HeHeliumGlows peachy-orange in a tube
Atomic number
2
Atomic mass
4.0
Lighter than air, which is why it's used to fill balloons and airships — and why breathing it makes your voice sound squeaky (don't try this, it's not safe in large amounts).
Why don't they react? Every noble gas already has a full outer shell of electrons. Atoms bond with each other to fill up empty space in that outer shell — noble gases have no empty space to fill, so they mostly keep to themselves.
1. Which noble gas is used to fill party balloons?
2. Which gas glows red-orange in signs?
3. Which gas is often used inside regular lightbulbs to stop the filament burning out?
4. What do all noble gases have in common?
5. Which noble gas is radioactive and can seep from rock into basements?