How can I write underset tag properly in the reaction?

I am using mhchem package for writing chemical reactions in my blog. How shall I use the underset tag properly so that the text hydrogen ion will come just below the product?

Code I have tried is below:

\ce{H – e^–>\underset{\text{Hydrogen ion}}{\ce{H^+}}


You have

• – instead of - (twice)
• missing spaces around the arrow (and a missing dash): ->
• missing $...$ around underset{}{}
• a missing } at the end.

Correcting all this gives:

\documentclass{article}
\usepackage[version=4]{mhchem}
\begin{document}
\ce{H - e^- -> $\underset{\text{Hydrogen ion}}{\ce{H^+}}$}
\end{document}