\begin{table}%t4
\caption {\label{t4}The average abundances for M~22 stars.}
%\centering
\par
\begin{tabular}{ l r c c}
\hline\hline
El.   & Abundance [dex] & $\sigma_{\rm obs}$ & ${N_{\rm stars}}$ \\
\hline
$ [\rm  O/Fe]$       &   0.28~$\pm$~0.05 & 0.20 & 17 \\
$ [\rm Na/Fe]$       &   0.24~$\pm$~0.08 & 0.30 & 17 \\
$ [\rm Mg/Fe]$       &   0.39~$\pm$~0.03 & 0.11 & 17 \\
$ [\rm Al/Fe]$       &   0.34~$\pm$~0.08 & 0.31 & 17 \\
$ [\rm Si/Fe]$       &   0.43~$\pm$~0.01 & 0.03 & 17 \\
$ [\rm Ca/Fe]$       &   0.31~$\pm$~0.02 & 0.07 & 17 \\
$ [\rm Sc/Fe]_{ScII}$ &   0.04~$\pm$~0.01 & 0.04 & 17 \\
$ [\rm Ti/Fe]_{TiI}$  &   0.24~$\pm$~0.01 & 0.06 & 17 \\
$ [\rm Ti/Fe]_{TiII}$ &   0.34~$\pm$~0.01 & 0.06 & 17 \\
$ [\rm  V/Fe]$       &$-$0.09~$\pm$~0.02 & 0.10 & 17 \\
$ [\rm Cr/Fe]$       &$-$0.13~$\pm$~0.02 & 0.08 & 17 \\
$ [\rm Fe/H ]$       &$-$1.76~$\pm$~0.02 & 0.10 & 17 \\
$ [\rm Ni/Fe]$       &$-$0.07~$\pm$~0.01 & 0.04 & 17 \\
$ [\rm  Y/Fe]_{YII}$  &   0.05~$\pm$~0.07 & 0.27 & 17 \\
$ [\rm Zr/Fe]_{ZrII}$ &   0.36~$\pm$~0.06 & 0.23 & 17 \\
$ [\rm Ba/Fe]_{BaII}$ &   0.19~$\pm$~0.06 & 0.23 & 17 \\
\hline
\end{tabular}
\end{table}