Merging curved arrows in chemfig (or tikz?)

Question

I'm fairly new to Latex and I've been using chemfig to draw a couple of diagrams so far, but for this one I'm trying to do I've not found a way. I haven't used tikz before, but it seems to me that it would be the better option here. Nevertheless I can't find any example of what I'm looking for anywhere so I thought I would just ask.

Basically what I want to do is this:

But I haven't been able to come even close and don't have a single line of code to show for it. Can anyone help?

EDIT: I've very clumsily thrown together this following code, which is kind of what I wanted, but I'm hoping there's a neater way to do it. Also I would very much like the arrows to touch/merge in some way.

\documentclass{scrartcl}
\usepackage{tikz-cd}
\begin{document}

\begin{tikzpicture}
\node (a) at (0,0) {A};
\node (b) at (2,0) {B};
\draw[-latex,bend right]  (a) edge (b);
\end{tikzpicture}\\
\begin{tikzpicture}
\node (c) at (0,0) {C};
\node (d) at (2,0) {D};
\draw[-latex,bend left]  (c) edge (d);
\draw[-latex,bend left]  (d) edge (c);
\end{tikzpicture}\\
\begin{tikzpicture}
\node (e) at (0,0) {E};
\node (f) at (2,0) {F};
\draw[-latex,bend right]  (f) edge (e);
\draw[-latex,bend right]  (e) edge (f);
\end{tikzpicture}\\
\begin{tikzpicture}
\node (g) at (0,0) {G};
\node (h) at (2,0) {H};
\draw[-latex,bend left]  (g) edge (h);
\end{tikzpicture}


\end{document}

Answer 1

You only need to draw the \nodes (A,B,C,...) and the arcs. To draw an arc you need to write

\draw (1,2) arc (0:90:3);

which means that you are drawing an arc starting at point (1,2) with inital angle 0, ending angle 90 and radius 3.

Something like this:

\documentclass[border=2mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{babel} % just in case
\begin{document}
\begin{tikzpicture}[y={(0,-1cm)}, shorten >= 2mm, shorten <= 2mm,]
  \def\s{1} % separation between nodes
  \node (A) at ( 0,   0) {$A$};
  \node (B) at (\s,   0) {$B$};
  \node (C) at ( 0,  \s) {$C$};
  \node (D) at (\s,  \s) {$D$};
  \node (E) at ( 0,2*\s) {$E$};
  \node (F) at (\s,2*\s) {$F$};
  \node (G) at ( 0,3*\s) {$G$};
  \node (H) at (\s,3*\s) {$H$};
  \draw[->] (A) arc (180:  0:0.5*\s);
  \draw[->] (C) arc (180:360:0.5*\s);
  \draw[->] (D) arc (  0:180:0.5*\s);
  \draw[->] (E) arc (180:  0:0.5*\s);
  \draw[->] (F) arc (360:180:0.5*\s);
  \draw[->] (H) arc (360:180:0.5*\s);
\end{tikzpicture}
\end{document}

will draw: