\begin{table}%t2
\par
  \caption{\label{tab_atom}Statistics of the model atoms used in our disc models.} 
    %\centering
\par
    \small\begin{tabular}{lrrr}
      \hline\hline
      Ion & LTE levels & NLTE levels & Lines\\
     \hline
   H~{\sc i}    &      6     &       10    &     45 \\  
   H~{\sc ii}   &      $-$   &        1    &      $-$  \\ 
   He~{\sc i}   &     15     &       29    &     61  \\ 
   He~{\sc ii}  &     24     &        8    &     28  \\ 
   He~{\sc iii} &      $-$   &        1    &      $-$  \\ 
   C~{\sc i}    &     14     &        7    &      4  \\ 
   C~{\sc ii}   &      4     &       38    &    160  \\ 
   C~{\sc iii}  &      9     &       58    &    329  \\ 
   C~{\sc iv}   &     49     &        9    &     17  \\ 
   C~{\sc v}    &      0     &        1    &      0  \\ 
   N~{\sc i}    &     15     &       12    &     15  \\ 
   N~{\sc ii}   &      4     &       17    &     21  \\ 
   N~{\sc iii}  &     38     &        7    &      5  \\ 
   N~{\sc iv}   &     78     &       16    &     30  \\ 
   N~{\sc v}    &      8     &       54    &    297  \\ 
   N~{\sc vi}   &      0     &        1    &      0  \\ 
   O~{\sc i}    &     12     &        1    &      0  \\ 
   O~{\sc ii}   &     14     &       29    &     82  \\ 
   O~{\sc iii}  &      8     &       36    &     42  \\ 
   O~{\sc iv}   &     58     &       11    &      5  \\ 
   O~{\sc v}    &     15     &        6    &      4  \\ 
   O~{\sc vi}   &      0     &        1    &      0  \\ 
   Si~{\sc ii}  &      5     &       25    &     28  \\ 
   Si~{\sc iii} &     17     &       17    &     27  \\ 
   Si~{\sc iv}  &     11     &       28    &     49  \\ 
   Si~{\sc v}   &     44     &       15    &     20  \\ 
   Si~{\sc vi}  &      0     &        1    &      0  \\ 
\hline
    \end{tabular}
\end{table}