Chemfig: How to Make the Boundry of an Atom be Circular?

Question

I am using \makebox to control how atoms are printed for consistent results. I would like to print my atoms as a circle instead of a box so that all bonds at all angles will be equidistant from the boundaries of the atom. I noticed that the \charge command has an option to print charges along a circular boundary; however, there isn't a similar option for the \chemfig command. Is there a command like \makebox that produces a circular boundry or would there be another way to accomplish this goal? See the below demonstrations.

\documentclass[border=10pt]{standalone}
\usepackage{adjustbox}
\usepackage{chemfig}

\begin{document}
%
    \def\foreverunspace{%
      \ifnum\lastnodetype=11
        \unskip\foreverunspace
      \else
        \ifnum\lastnodetype=12
          \unkern\foreverunspace
        \else
          \ifnum\lastnodetype=13
            \unpenalty\foreverunspace
          \fi
        \fi
      \fi
    }%
%
    \renewcommand{\printatom}[1]{%
        \setbox0=\hbox{#1\foreverunspace}\ifdim\wd0=0pt% if the argument doesn't have a size
            \ensuremath{\mathrm#1}%
        \else%
            \makebox(2.5ex,2.5ex){\ensuremath{\mathrm#1}}% use makebox for atoms
        \fi%
    }%
%
    \setchemfig{%
        % circle=true% not a defined key!
        fixed length=false%
    }%
    \noindent%
    \chemfig{%
        C%
            (-[:0]F)%
            (-[:45]F)%
    }%
%
    \setchemfig{debug=true}%
    \chemfig{%
        C%
            (-[:0]F)%
            (-[:45]F)%
    }%
%
    \hspace{2ex}%
%
    \setchemfig{debug=false}%
    \chemfig{\charge{[overlay=false]0=\:,45=\:}{O}}\hspace{2ex}%
%
    \setcharge{debug=true}%
    \chemfig{\charge{[overlay=false]0=\:,45=\:}{O}}\hspace{2ex}%
%
    \setcharge{debug=false,circle=true}%
    \chemfig{\charge{[overlay=false]0=\:,45=\:}{O}}\hspace{3ex}%
%
    \setcharge{debug=true}%
    \chemfig{\charge{[overlay=false]0=\:,45=\:}{O}}
%
\end{document}

Answer 1

I defined two pic objects. One has the border always drawn and is simpler. It is named atom and has two arguments: its name and the list of angles of the small bullets, if any. The other one, atom o depends on three arguments; its third defines the opacity of the border. The top element in the figure is given by atom o.

So what do you think? Note that other decorations may be similarly added.

The code

\tikzset{%
  pics/atom/.style 2 args={%  name, list of angles (charges?)
    code={%
      \path (0, 0)
      node[circle, draw,
      minimum width=6.6ex, minimum height=6.6ex,
      inner sep=1ex, outer sep=1ex,
      text=black] (#1) {$#1$};
      \foreach \i in {#2}{%
        \filldraw[black] (\i: 3.3ex) circle (.25ex);
      }
    }
  },  
  pics/atom o/.style n args={3}{%  name, list of angles, border's opacity
    code={%
      \path (0, 0)
      node[circle, draw, opacity=#3, text opacity=1,
      minimum width=6.6ex, minimum height=6.6ex,
      inner sep=1ex, outer sep=1ex,
      text=black] (#1) {$#1$};
      \foreach \i in {#2}{%
        \filldraw[black] (\i: 3.3ex) circle (.25ex);
      }
    }
  }
}

\begin{tikzpicture}
  \path (0, 0) pic {atom={F}{0, 30}};
  \path (2, 0) pic[red] {atom={He}{90}};
  \path (F) edge[-] (He);

  \path (2, 2) pic[blue] {atom o={O}{80, 110, 180}{.2}};
\end{tikzpicture}

\end{document}