# Is “double dot” (“··”) notation used for a double radical?

I wondered if this was a typo in the notes given to me. I haven’t come across notation like this before:

Branching — steps in which number of radicals increases (can lead to explosion)

$$\ce{H^. + O2 -> OH^. + O^{..}}$$

• Alone, the oxygen atom has always two separated uncoupled electrons. It never lasts a long time like this, but It has two doublets and two independent electrons in the outer shell. This makes a total of $6$ electrons. On the other hand, the molecule $\ce{O2}$ is a double radical, with one free electron on either Oxygen atoms.. – Maurice Apr 27 at 16:16
• Ahh, that makes sense. Thank you so much for this – Marina Calder Apr 27 at 16:42
• It's call diradical or biradical, just saying ;) – Mithoron Apr 27 at 20:51
• @MarinaCalder If you got your answer, feel free to self-answer it. Self-answering is always appreciated and it will help future readers. – Nilay Ghosh May 8 at 10:15