Across
- 3. Which planet is most similar to Earth?
- 4. What is the type of element that has 13 protons?
- 7. What is the first artificial element?
- 9. How many nonmetals are there in the periodic table?
- 10. Which is the last element in the periodic table?
- 12. Which animal was the first to go into space?
- 13. Which noble gas is in the 4th period of the periodic table?
- 15. Which element has 22 protons?
Down
- 1. How many of the elements in the periodic system are found in nature?
- 2. What is the structural unit of DNA?
- 5. How are the elements in the periodic table arranged?
- 6. Which scientist first proposed the periodic table?
- 8. 2nd largest planet in the solar system?
- 11. How many planets larger than Earth are there in the solar system?
- 14. What period is mercury in in the periodic table?