| Answer | Crossword Clue |
|---|---|
| GAS | Nitrogen or helium |
| GAS | Neon or helium |
| INERTGAS | Neon or helium |
| INERTGAS | Helium or neon |
| INERTGAS | Helium or krypton |
| ELEMENT | Helium or hydrogen |
| GAS | Methane or helium |
| GAS | Helium or neon |
| GAS | Argon or helium |
| GAS | Hydrogen or helium |
| ELEMENT | Hydrogen or helium |
| GAS | Helium or hydrogen |
| GAS | Oxygen or helium |
| GAS | Helium or oxygen |
| INERT | Like argon or helium |
| INERT | Like helium or argon |
| INERT | Like neon or helium |
| INERT | Like helium or neon |
| ATNO | 1 for hydrogen or 2 for helium: Abbr. |
| superfluidity | The property of flowing without friction or viscosity, as in liquid helium below about 2.18 kelvins |
