\begin{center}
\begin{pspicture}(-4,-3)(4.5,5.5)
\psset{lightsrc=100 10 -20,lightintensity=3,viewpoint=200 30
20 rtp2xyz,Decran=40,} 
\psframe(-4,-3)(4.5,5.5)
{\psset{linewidth=0.5\pslinewidth}
\codejps{
/Soufre1 {3.56  [20 16] newsphere
 dup (Yellow) outputcolors} def
/Soufre2 {3.56  [20 16] newsphere
 {0 0.000 20.10 translatepoint3d} solidtransform
 dup (Yellow) outputcolors} def
% Liaison simple
/LiaisonR {
     7.5 0.5 15  [10 10] newcylindre
      dup (Red) outputcolors
   } def
/LiaisonY {
     0 0.5 7.5  [10 10] newcylindre
      dup (Yellow) outputcolors
   } def
% fin Liaison simple
/Liaison{LiaisonR LiaisonY solidfuz} def
/Ox {2.17  [20 16] newsphere
     {0 0 15 translatepoint3d} solidtransform
     dup (Red) outputcolors} def
/LO { Liaison Ox solidfuz} def
/LO1 { LO  {0 -109.5 0 rotateOpoint3d} solidtransform } def
/LOx1 { LO1  {0 0 120 rotateOpoint3d} solidtransform } def
% fin liaison simple S-O
% Liaison double S=O
/LiaisonD1 {Liaison {-0.75 0 0 translatepoint3d} solidtransform} def
/LiaisonD2 {Liaison {0.75 0 0 translatepoint3d} solidtransform} def
/LiaisonDD { LiaisonD1 LiaisonD2 solidfuz} def
/LiaisonDOx {LiaisonDD Ox solidfuz} def
/LiaisonDOx1 {LiaisonDOx {0 -109.5 0 rotateOpoint3d} solidtransform } def
/LiaisonDOx2 {LiaisonDOx1 {0  0 -120 rotateOpoint3d} solidtransform } def
/LO12 { LiaisonDOx1 LiaisonDOx2 solidfuz} def
/LO123 {LO12 LOx1 solidfuz} def
% liaison simple S-S
/L4 { 0 0.5 20.10  [16 10] newcylindre
      dup (Yellow) outputcolors
    } def
/S1L4{ Soufre1 L4 solidfuz} def
/S1S2L4{ S1L4 Soufre2 solidfuz} def
/S2O3 { S1S2L4 LO123 solidfuz} def
S2O3  drawsolid**}
\axesIIID(0,0,0)(25,20,25)}
\psPoint(0,0,20.1){S2}
\psPoint(-14.14,0,-5){O1}
\psPoint(7.07,-12.24,-5 ){O2}
\psPoint(7.07,12.24,-5 ){O3}
\pcline[linestyle=dotted]{<->}(O2)(O)
\aput{:U}{15 pm}
\pcline[linestyle=dotted]{<->}(O)(S2)
\aput{:U}{\small 20,1 pm}
\pcline[linestyle=dotted]{<->}(O2)(O3)
\lput*{:U}{\small 24,5 pm}
\pcline[linestyle=dotted]{<->}(O2)(S2)
\lput*{:U}{\small 28,8 pm}
\pstMarkAngle[arrows=<->,MarkAngleRadius=0.8,linestyle=dotted]{O2}{O}{O3}{\footnotesize 109,4$^{\mathrm{o}}$}
\pstMarkAngle[arrows=<->,MarkAngleRadius=0.8,linestyle=dotted]{O1}{O}{S2}{\footnotesize 109,5$^{\mathrm{o}}$}
\rput(0,-2.5){$\mathrm{S_2^{\phantom{2}}O_3^{2-}}$}
\end{pspicture}
\end{center}