Across
- 2. hydrdogen is one of the most________elements
- 5. most common source of hydrogen
- 8. percentage of all matter by mass in the universe that is hydrogen
- 10. hydrogen gas is ______in Earth's atmosphere because the atoms are light and escape gravity floating into space
- 11. hydrogen takes this place as the most abundant on Earth
- 12. hydrogen is the element from which all other elements are formed and a process start is in these
Down
- 1. hydrogen is in this position on the periodic table
- 3. the number of protons that give hydrogen the number one on the periodic table
- 4. percentage of all atoms in the universe that are hydrogen
- 6. another source of hydrogen besides hydrocarbons in fossil fuels
- 7. hydrogen's comparative weight compared with all the chemical elements
- 9. the type of element that hydrogen is