I am a Gas!

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Across
  1. 3. I am a noble gas, and I'm used to fill up party balloons and blimps.
  2. 5. I am a noble gas, and I'm used in flashlights and photographic flashes.
  3. 8. I am a noble gas, and I emit a brilliant reddish-orange color in advertising signs.
  4. 9. I am a gas that is vital for life on Earth. We can't live without it.
  5. 10. I make up 78 percent of the Earth's atmosphere.
  6. 11. Without me, humans cannot survive, and we wouldn't be here!
Down
  1. 1. I am a halogen, and I'm used to clean my teeth, and eliminate cavities.
  2. 2. I am a noble gas, and I'm used for arc welding and fluorescent lights.
  3. 4. I am a halogen, and I purify the water in swimming pools.
  4. 6. This gas is the most abundant element in the universe
  5. 7. I am a noble gas, and all of my isotopes are radioactive.
  6. 12. I am a noble gas, and like Krypton, I'm used for flashlights, but I'm also used in car headlamps and high density lamps.