Answer: Highly reactive atomic hydrogen formed in situ (not H2 gas).
- A Highly reactive atomic hydrogen formed in situ (not H2 gas)
- B Ordinary H2 gas simply compressed to high pressure
- C Deuterium gas generated by electrolysis of heavy water
- D Pure protium gas isolated from natural hydrogen
Correct answer: A. Highly reactive atomic hydrogen formed in situ (not H2 gas)
Explanation: Nascent hydrogen is freshly generated atomic H (before it dimerises to H2), highly reactive due to unpaired electron.
Each water molecule's O-H bonds (covalent, solid) can hydrogen-bond (dashed) to neighbouring molecules, forming an extended network responsible for water's unusually high boiling point and density anomaly.
Concept context
The simplest and most abundant element in the universe. Study its unique position in the periodic table, isotopes (protium, deuterium, tritium), properties of water and hydrogen peroxide, and industrial uses.