general knowledge

12345678910
Across
  1. 2. Gas we breathe (6)
  2. 5. Extinct reptile from millions of years ago
  3. 6. Person of enormous size (5)
  4. 8. Smallest building block of matter (5)
  5. 10. Colorful arc after rain (7)
Down
  1. 1. Ancient Egyptian tomb shape (6)
  2. 3. Mountain that erupts lava (7)
  3. 4. City where the government sits (7)
  4. 7. Musical instrument with keys (5)
  5. 9. Largest body of saltwater (6)