1 (1A) 2 (2A) 17 (7A) 18 (8A)
I gave my students this multiple choice question: Incandescent light bulb filaments are best preserved by filling the bulb with a low density, non-reactive gas. From which group of elements on the periodic table is this gas most likely selected?

Only one answer is correct among these 4 choices:
- 1 (1A)
- 2 (2A)
- 17 (7A)
- 18 (8A)

Could you tell me which one is correct?

18 (8A)