| Answer | Crossword Clue |
|---|---|
| TRIODE | Vacuum tube with three elements |
| TRIODES | Vacuum tubes containing three elements |
| TRIODE | Three-element vacuum tube |
| TRIODE | Three-part vacuum tube |
| DIODE | Electron tube with two elements |
| HALOGENS | Only group with elements in all three states of matter at room temperature |
