Group 18 of the Periodic Table
Group 18 of the periodic table (Noble gases) has 7 elements: Helium, Neon, Argon, Krypton, Xenon, Radon and Oganesson. Elements in a group have a similar last electron shell, so they show similar chemical properties. Moving down a group, the number of shells and the atomic radius usually increase.
Noble gases
The noble gases are the group 18 elements: their outer shell is full, so under normal conditions they are very unreactive.
Element list
| Atomic no. | Symbol | Name | Atomic mass | Phase | Short configuration |
|---|---|---|---|---|---|
| 2 | He | Helium | 4.0026 | Gas | 1s² |
| 10 | Ne | Neon | 20.18 | Gas | [He] 2s² 2p⁶ |
| 18 | Ar | Argon | 39.95 | Gas | [Ne] 3s² 3p⁶ |
| 36 | Kr | Krypton | 83.798 | Gas | [Ar] 3d¹⁰ 4s² 4p⁶ |
| 54 | Xe | Xenon | 131.29 | Gas | [Kr] 4d¹⁰ 5s² 5p⁶ |
| 86 | Rn | Radon | 222 | Gas | [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶ |
| 118 | Og | Oganesson | 294 | Solid (a theoretical prediction) | [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁶ |
Frequently asked questions
What are the group 18 elements of the periodic table?
The group 18 elements are Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn) and Oganesson (Og).
How many elements are in group 18?
Group 18 of the periodic table has 7 elements (excluding the lanthanides and actinides).