1.1. Hydrogen is a chemical element with symbol H and atomic number 1.
2. physical properties
2.1. colourless
2.2. odourless
2.3. tasteless
2.4. non-toxic
2.5. highly combustible
2.6. Color colorless
2.7. Phase (at STP) gas
2.8. Melting point 13.99 K (−259.16 °C, −434.49 °F)
2.9. Boiling point 20.271 K (−252.879 °C, −423.182 °F)
2.10. Density (at STP) 0.08988 g/L
3. history and discovery
3.1. in 1671, Robert Boyle discovered and described the reaction between iron filings and dilute acids, which results in the production of hydrogen gas.