\begin{table}%t2
\caption{Initial abundances of H$_2$ and elements \cite[]{graedel82a}.}
\label{tab1}
\small
%\centerline
{
\begin{tabular}{l c}
\hline\hline
%\noalign{\smallskip}
Species $i$ & $n_{i}/n_{\rm H}$ $^{\dag}$ \\
%\noalign{\smallskip}
\hline
%\noalign{\smallskip} 
H$_2$ & $0.5$ \\
%\noalign{\smallskip}
He & $0.14$ \\
%\noalign{\smallskip} 
C$^+$ & $7.3(-5)$ \\
%\noalign{\smallskip}
N & $2.14(-5)$ \\
%\noalign{\smallskip}
O & $1.76(-4)$ \\
%\noalign{\smallskip}
S$^+$ & $8.0(-8)$ \\
%\noalign{\smallskip}
Na$^+$ & $2.0(-9)$ \\
%\noalign{\smallskip}
Mg$^+$ & $7.0(-9)$ \\
%\noalign{\smallskip}
Si$^+$ & $8.0(-9)$ \\
\noalign{\smallskip}
P$^+$ & $3.0(-9)$ \\
%\noalign{\smallskip}
Cl$^+$ & $4.0(-9)$ \\
%\noalign{\smallskip}
Fe$^+$ & $3.0(-9)$ \\
%\noalign{\smallskip}
\hline
\end{tabular}}
\medskip
$^{\dag}$ $a(b) = a \times 10^{b}$.
\end{table}