# [texhax] units, chemistry and mhchem

Gordon Haverland ghaverla at materialisations.com
Thu Dec 29 15:10:46 CET 2011

On December 29, 2011, Simmie, John wrote:
> Chemists use a superscript bullet to denote an unpaired
> electron or the construct \.{C} or $\dot{C}H_3$ MHCHEM cannot
> do this ... the author of the package was reluctant to take my
> word that that is what we chemists use.
>
> Also we use two superscript dots over the element symbol  to
> denote a carbene, thus \"{C}

Most of the chemistry I've been writing of late is of the nuclear
variety (I come from materials science and engineering).  I don't
think I've ever had to note unpaired electrons in a chemical
formula.  The NIST recommendations for nuclear metastable states
are different than I commonly have commonly seen: Sc-46m I
normally see as \isotope[46m]{Sc}.  The version of isotope I have
been using seems old, maybe the new one corresponds with the NIST
document?

I suppose our (MSE) oddball unit will still come out kind of
screwy with siunitx (\SI{15}{MPa.m\tothe{0.5}})?  It isn't
mentioned in the NIST document.

In the mhchem documentation, I actually like the examples where
serif and sans serif are mixed.

Taking John Simmie's example of a dangling bond for inspiration, I
would disagree with the NIST recommendation on nuclear metastable
states.  For example, if we are working with

\ce{^{180}Ta^m5+}

it looks wrong to have the m after the elemental symbol to me.
I've no idea if that typesets correctly.  What looks better using
mhchem (to me) is

\ce{^{180m}Ta^5+}

But this has been an enlightening topic.

--
Gord