Group 0 — the noble gases

Group 0 (also called Group 8 or Group 18) sits on the right of the periodic table: helium, neon, argon, krypton, xenon, radon.

Electron configurations

All noble gases have a full outer shell of electrons:

• Helium: 2 (full first shell)
• Neon: 2,8
• Argon: 2,8,8
• Krypton: 2,8,18,8

Because they already have a full outer shell, they have no tendency to gain, lose, or share electrons — they are extremely unreactive (inert).

Physical properties

• All are colourless gases at room temperature.
• All exist as monatomic atoms (single atoms, not molecules).
• Densities and boiling points increase down the group as atomic mass / number of electrons increases (stronger inter-atomic forces).

Element	Boiling point (°C)	Density (g/dm³ at STP)
Helium	-269	0.18
Neon	-246	0.90
Argon	-186	1.78
Krypton	-153	3.75

Uses

• Helium — balloons, airships (low density, non-flammable, safer than hydrogen).
• Neon — advertising signs (glows red-orange when electrified).
• Argon — fills incandescent light bulbs (inert, prevents filament oxidation).
• Krypton / xenon — high-performance lamps, lasers.

WJEC exam tip

When asked why argon is used in light bulbs, give two pieces of reasoning: (i) it is unreactive / inert, so it does not react with the hot tungsten filament, AND (ii) it prevents oxygen reaching the filament, stopping it burning out. One reason alone usually scores only B1.