# What are the essential arrows for entering chemical equations in text?

I'm the author of a custom chemistry keyboard on iOS. I am looking at improving the selection of Unicode arrows I can provide. When the device is a phone in portrait mode, I don't have a lot of extra room on screen, so I give a flyout with:

# →, ⇌, ↔, ⇢, ↛

When the phone is rotated or it's on a larger device, I have some extra room, so I was thinking about adding either more items in that flyout, or perhaps another button with an expanded set. Maybe something like:

# ⇄, ←, ↝, ↮⟿

I would like to make the most useful unicode arrows available, and not provide ones that nobody would use. I expect that this will vary from speciality to speciality, but I'd really appreciate some feedback.

I'm limited to what is in Unicode. (If you are on a Mac, you can bring up the Emoji and Symbols palette and look at the Arrows category)

• I'd go with $\rightarrow,\leftarrow,\leftrightarrow,\text{ and }\rightleftarrows$. The rest are rarely needed anyway. – Ivan Neretin Jul 31 '17 at 11:24
• Still there are some usecases that cannot be covered with Unicode, e.g. I don't think there is an arrow for isolobality, which might come in handy sometimes, also how would one denote reaction conditions, which are typically written within the arrow? I would agree with @IvanNeretin that the basic set is good enough and for more advanced writings user will use other tools. – andselisk Jul 31 '17 at 11:29
• Yeah, conditions is a big thing. $\stackrel{\Delta}{\longrightarrow}$ is much more useful than $\rightsquigarrow$. – Ivan Neretin Jul 31 '17 at 11:48
• It seems like there is some distinction between the ⇄ and the ⇌ characters. Which is more useful? – Glenn Howes Jul 31 '17 at 11:57
• I can see the value of this, but its highly subjective and dependant on the type/level of chemistry involved. It would perhaps be better off discussed on chat... – NotEvans. Jul 31 '17 at 11:58