Argon - first version, Bismuth - internal, Carbon - second version for the public if I had to make a wild guess.
This naming strategy is bizarre.
There are no good elements for D; Dysprosium is the only one, and it's a mouthful. There are no good elements for E; Europium is the only one and would seem political. Is Fluorine their next release? (And then Gallium or Gadolinium?)
After Carbon, they should just update to Gemini 4.1 or 4.5 or whatever, and drop the random unrelated elements.
Clearly, Google has already fired their marketing department and Gemini sucks at this job.
Maybe it thought the names are clear and intuitive (for an LLM perhaps).
Other sources say that what was publicly released as Argon was already the second version named Barium internally. So there was a separate internal Argon and public Argon was Barium. Not confusing at all for them! https://www.reddit.com/r/GeminiAI/comments/1x292ly/a_new_che...