Periodic Table

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Across
  1. 3. Toxic to life because of its unbelievable reactivity
  2. 4. One of the main ingredients in some very strong acids
  3. 5. The most abundant element by weight in all living organisms
  4. 8. A dull brown metal that nobody cares about
Down
  1. 1. The second most common element on Earth
  2. 2. The first radioactive element in the periodic table
  3. 6. Essential to life, but toxic in high amounts
  4. 7. A very conductive metal used in electronics