Question: just wanted to create a table, that looks something like the following

![table](https://i.imgur.com/YABzM4O.jpg) 

First and second row are no problem at all, but the third row is difficult. I can't achieve this special alignment.

Thanks in advance

Answer: 
I guess the semi-tricky thing about the table is that whereas the columns' contents are all left-aligned, the numbers are -- depending on point of view -- either right-aligned or aligned on their decimal points/commas. 

To achieve the desired look, you could use

* the `tabularx` package and a modified form of its `X` column type to generate left-aligned entries while automatically breaking lines in the table's header, and
* "phantoms" to insert whitespace where needed. Since three instances of such a need occur just on the third line, it's handy to create a shortcut macro for this task, e.g., to set `\newcommand\ph{$\phantom{1}$}`.

![enter image description here](https://i.stack.imgur.com/lXoep.png)

```
\documentclass{article}
\usepackage{booktabs,tabularx}
\newcolumntype{Y}{>{\raggedright\arraybackslash}X}
\newcommand\ph{$\phantom{1}$} % a handy shortcut
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{newtxtext,newtxmath} % looks like the font is use is "Times Roman"
\begin{document}
\noindent
\begin{tabularx}{0.6\textwidth}{@{} YYY @{}}
\toprule
\textbf{Wellenlänge} & \textbf{Spezifische Absorption} & \textbf{Maximale Abweichung}\\
\textbf{(nm)} & $\mathbf{A}^{1\,\%}_{1\,\text{cm}}$\\
\midrule
235 &   124,5   &   122,9 --   126,2 \\
257 &   144,5   &   142,8 --   146,2 \\
313 & \ph48,6   & \ph47,0 -- \ph50,3 \\
350 &   107,3   &   105,6 --   109,0 \\
\bottomrule
\end{tabularx}
\end{document}

```
There are some ways to get this layout, one already proposed by Ian Thompson using `\phantom`, also shown here or using extra columns with automatic filling of the `-` characters in the 3rd logical column from the screen shot.

```
\documentclass[12pt]{article}
\usepackage{array}

\begin{document}

\begin{center}
\begin{tabular}{lrr}
\hline
\textbf{Wellenl\"ange}  & \textbf{Spezifische}  & \multicolumn{1}{l}{\textbf{Maximale}} \tabularnewline
               & \textbf{Absorption} & \multicolumn{1}{l}{\textbf{Abweichung}} \tabularnewline
\textbf{(nm) } & & \tabularnewline
\hline
235 & 124,5 & 122,9 -- 126,2 \tabularnewline
257 & 144,5 & 142,8 -- 146,2 \tabularnewline
313 & 48,6 &  \phantom{1}47,0 -- \phantom{1}50,3 \tabularnewline
350 & 107,3 & 105,6 -- 109,0 \tabularnewline
\hline
\end{tabular} \par
\end{center}

\begin{center}
\begin{tabular}{lrrl@{--}lr}

\hline
\textbf{Wellenl\"ange}  & \textbf{Spezifische}  & \multicolumn{4}{l}{\textbf{Maximale}} \tabularnewline
               & \textbf{Absorption} & \multicolumn{4}{l}{\textbf{Abweichung}} \tabularnewline
\textbf{(nm) } & & \multicolumn{4}{l}{} \tabularnewline
\hline
235 & 124,5 & 122,9 &  & & 126,2 \tabularnewline
257 & 144,5 & 142,8  & & & 146,2 \tabularnewline
313 & 48,6 &  47,0 & & &  50,3 \tabularnewline
350 & 107,3 & 105,6 & & &  109,0 \tabularnewline
\hline
\end{tabular}

\end{center}

\end{document}

```

![enter image description here](https://i.stack.imgur.com/eEdct.jpg)