# Example: The electric dipole moment (p) in the water molecule

Published 2011-12-31 | Author: Jimi Oke

The diagram shows the geometry of hydrogen and oxygen atoms in the water molecule, and the position of the dipole (p). Using known dimensions, we can calculate the energy of the dipole, and, consequently, the interaction energy between two molecules.

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% The electric dipole moment (p) in the water molecule
% Author: Jimi Oke
\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[>=latex,scale=1.3]
\shade[ball color=gray!10!] (0,0) coordinate(Hp) circle (.9) ;
\shade[ball color=gray!10!] (2,-1.53) coordinate(O) circle (1.62) ;
\shade[ball color=gray!10!] (4,0) coordinate(Hm) circle (.9) ;
\draw[thick,dashed] (0,0) -- (2,-1.53) -- (4,0) ;
\draw[thick] (2,.2) -- (2,1.5) node[right]{$\mathbf{p}$} ;
\draw (2.48,-1.2) arc (33:142:.6)  ;
\draw (2,-.95) node[above]{$105^{\circ}$} ;
\draw (0,.2) node[left]{H$^+$} ;
\draw (4,.2) node[right]{H$^-$} ;
\draw (2,-1.63) node[below]{O$^{2-}$} ;
\foreach \point in {O,Hp,Hm}
\fill [black] (\point) circle (2pt) ;
\end{tikzpicture}
\end{document}


• #1 Sven, March 1, 2012 at 6:32 p.m.

...is the charge of the right H correct? I'd guess the overall charge should be neutral!?

• #2 Yan, March 9, 2012 at 4:23 p.m.

Negative charge of a right hydrogen atom is definitely a bug.

• #3 Jimi Oke, March 14, 2012 at 2:19 p.m.

Oops! You are both right. Should be "H+". That must have been a typo on my part. I'll ask Stefan K. to see if this can be fixed!