Periodic Table

123456
Across
  1. 1. Which orange greens as it oxidizes?
  2. 4. What do humans and fish breathe?
  3. 5. What is commonly found in commercial salt?
  4. 6. What caused watch factory shutdowns in the early 1900's?
Down
  1. 2. Which element was discovered in 1898 by Marie Curie and her husband but is not radium?
  2. 3. Which gas is commonly used in colorful light fixtures?