\begin{longtable}{XX>{\ttfamily\textbackslash}XXXX>{\ttfamily\textbackslash}XX}
 \caption{predefined preficies}\\
 \toprule
 \emph{name}&\emph{prefix}&\multicolumn{1}{X}{\emph{macro}}&\emph{value}&
 \emph{name}&\emph{prefix}&\multicolumn{1}{X}{\emph{macro}}&\emph{value}\\
 \midrule\endfirsthead
 \caption{predefined preficies}\\
 \toprule
 \emph{name}&\emph{prefix}&\multicolumn{1}{X}{\emph{macro}}&\emph{value}&
 \emph{name}&\emph{prefix}&\multicolumn{1}{X}{\emph{macro}}&\emph{value}\\
 \midrule\endhead
 yocto & \yocto  &yocto  &  $10^{-24}$& zepto & \zepto  &zepto  &  $10^{-21}$\\
 atto  & \atto   &atto   &  $10^{-18}$& femto & \femto  &femto  &  $10^{-15}$\\
 pico  & \pico   &pico   &  $10^{-12}$& nano  & \nano   &nano   &  $10^{-9}$\\
 micro & \micro  &micro  &  $10^{-6} $& milli & \milli  &milli  &  $10^{-3}$\\[1ex]
 centi & \centi  &centi  &  $10^{-2} $& deci  & \deci   &deci   &  $10^{-1}$\\[1ex]
 deca  & \deca   &deca   &  $10^{+1} $& hecto & \hecto  &hecto  &  $10^{+2}$\\[1ex]
 kilo  & \kilo   &kilo   &  $10^{+3} $& mega  & \mega   &mega   &  $10^{+6} $\\
 giga  & \giga   &giga   &  $10^{+9} $& tera  & \tera   &tera   &  $10^{+12}$\\
 peta  & \peta   &peta   &  $10^{+15}$& exa   & \exa    &exa    &  $10^{+18}$\\
 zetta & \zetta  &zetta  &  $10^{+21}$& yotta & \yotta  &yotta  &  $10^{+24}$\\
 \bottomrule
 \end{longtable}