\begin{table}%t2
%\centering
\par
\caption{ Electron density indicators in \ngc.\label{tab2}}
\begin{tabular}{lcccc}
\hline
\hline
Ion &Ioniz. & Lines& Observed &$N_{{\rm e}}$ \\
&Pot. (eV) & used  & ratio & (cm$^{-3}$)\\
\hline
\ion{[S}{ii]} & 10.4 & 6731/6716 & 1.83 & 5000\\
\ion{[O}{ii]} & 13.6 & 3626/3729 & 1.90 & 3500\\
\ion{[S}{iii]} & 23.3 & 33.5/18.7 & 0.437 & 3300\\
\ion{[Cl}{iii]} & 23.8 & 5538/5518 & 1.80 & 10~000\\
\ion{[O}{iii]}  & 35.1 & 51.8/88.4 & 3.37 & 2000 \\
\hline
\end{tabular}
\end{table}