Paste code

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{textcomp}
\usepackage[italian]{babel}
\usepackage[
  a4paper,
  margin=15mm,
  bindingoffset=2mm,
  heightrounded,
]{geometry}

\usepackage{amsmath}
\usepackage{chemfig}
\usepackage[version=3]{mhchem}

\begin{document}

\schemestart
\chemfig{@{H1}H-[:30]@{O1}O-[:-30]@{H2}H}
\schemestop
\chemmove{\draw[blue,-latex]([yshift=2.2mm]H1.north)--([yshift=1.2mm,xshift=-1mm]O1.north west);}
\chemmove{\draw[blue,-latex]([yshift=2.2mm]H2.north)--([yshift=2.2mm,xshift=-1mm]O1.north east);}
\end{document}