How to correctly connect nodes in tabular

Question

I would like the nodes created in the table to be connected by a line. Ideally, the lines connect from the right-middle edge of the border for the nodes on the left, and the left-middle edge of the border for the nodes on the right. I've included the node connection listing at the end of the code. You can see that it clearly does not map properly onto the table.

\documentclass{article}
\usepackage{booktabs}
\usepackage{tikz}
\usepackage{array}
\newcommand\mybox[2]{\tikz[remember picture]{\node (#2) [draw=black, inner sep=4pt, anchor=text, rounded corners=1mm] {#1};}}
\setlength{\tabcolsep}{0.5in}
\setlength{\extrarowheight}{0.3in}
\begin{document}
\begin{tabular}{rl}
\mybox{Molecular}{molecular} & \mybox{Diamond}{diamond} \\
\mybox{Amorphous}{amorph} & \mybox{Sodium}{na} \\
\mybox{Metallic}{metal} & \mybox{Carbon Dioxide}{carbondiox} \\
\mybox{Covalent Network}{covnet} & \mybox{Glass}{glass}
\end{tabular}
\begin{tikzpicture}
\draw (molecular) -- (carbondiox);
\draw (amorph) -- (glass);
\draw (metal) -- (na);
\draw (covnet) -- (diamond);
\end{tikzpicture}
\end{document}

Answer 1

You need remember picture and overlay keys to your tikzpicture environment, to control where lines are connected just change (molecular) to (molecular.east ) or any anchor of node west, north, south, north east, north west, ...

\documentclass{article}
\usepackage{booktabs}
\usepackage{tikz}
\usepackage{array}
\newcommand\mybox[2]{\tikz[remember picture]{\node (#2) [draw=black, inner sep=4pt, anchor=text, rounded corners=1mm] {#1};}}
\setlength{\tabcolsep}{0.5in}
\setlength{\extrarowheight}{0.3in}
\begin{document}
\begin{tabular}{rl}
\mybox{Molecular}{molecular} & \mybox{Diamond}{diamond} \\
\mybox{Amorphous}{amorph} & \mybox{Sodium}{na} \\
\mybox{Metallic}{metal} & \mybox{Carbon Dioxide}{carbondiox} \\
\mybox{Covalent Network}{covnet} & \mybox{Glass}{glass}
\end{tabular}
\begin{tikzpicture}[remember picture,overlay]
\draw (molecular.east) -- (carbondiox.west);
\draw (amorph.east) -- (glass.west);
\draw (metal.east) -- (na.west);
\draw (covnet.east) -- (diamond.west);
\end{tikzpicture}
\end{document}  

Answer 2

It is also feasible with pure TikZ without overlays.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}
\begin{document}
\begin{tikzpicture}[
  column 1/.style={anchor=east},
  column 2/.style={anchor=west},
  ]
  \matrix[
  matrix of nodes,
  nodes={draw=black,inner sep=4pt,rounded corners=1mm},
  row sep=.5cm, column sep=1cm,
  ] (m) {
    Molecular        & Diamond        \\
    Amorphous        & Sodium         \\
    Metallic         & Carbon Dioxide \\
    Covalent Network & Glass          \\
  };
  \draw (m-1-1.east) -- (m-3-2.west);
  \draw (m-2-1.east) -- (m-4-2.west);
  \draw (m-3-1.east) -- (m-2-2.west);
  \draw (m-4-1.east) -- (m-1-2.west);
\end{tikzpicture}
\end{document}