氕

氕 (Kangxi radical 84, 气+1, 5 strokes, cangjie input 人弓中 (ONL), four-corner 8021₇, composition ⿹气丿)

• Kangxi Dictionary: not present, would follow page 599, character 3
• Hanyu Da Zidian (first edition): volume 3, page 2010, character 2
• Unihan data for U+6C15

Ideogrammic compound (會意／会意) : 气 (“gas”) + 丿 (“one”). Also a phono-semantic compound (形聲／形声) , where 丿 (piě) acts as the phonetic component. Compare 氘 (“deuterium”) and 氚 (“tritium”).

From 丿 (piě, “left falling stroke”) from the glyph, possibly influenced by New Latin protium. In Mandarin, it is pronounced in the first tone by analogy with 氘 (dāo, “deuterium”) and 氚 (chuān, “tritium”).

氕

1. protium

• 氘 (dāo, “deuterium”)
• 氚 (chuān, “tritium”)
• 氫／氢 (qīng, “hydrogen”)