\documentclass{article}
\usepackage{chemformula}

\begin{document}

\ch{M -> M^{n+} + ne^{-}}
\ch{A + B ->[a] C}

\ch[options]{input}
\ch[decimal-marker={,}]{3.5}
\ch[frac-style=xfrac]{3/2}

\ch{ "escaped text" }
\ch{ 'escaped text' }
\ch{"\ldots\," Na + "\ldots\," Cl2 -> "\ldots\," NaCl}

\ch{ $escaped math$ }
\ch{ \(escaped math\) }
\ch{$2n$ Na + $n$ Cl2 -> $2n$ NaCl}

\begin{equation}
  \ch{M -> M^{n+} + ne^{-}}
\end{equation}

\footnote{For these citations, see Stephen's quotation.}

\end{document}