如何插入大括号、箭头交叉等

Question

由于英语不是我的母语，我不知道如何正确描述我的问题。但我有一张我想输入的图片。

这是我目前取得的进展：

\documentclass[a4paper]{article}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}
    Cr & 3\downarrow \arrow[rd] & 2Cr: & 6\downarrow \\
    C & 2\uparrow \arrow[ru]& 3C: & 6\uparrow
\end{tikzcd}
\end{document}
\

背景：在我的学校，我们用它来展示如何排列氧化还原反应。

Answer 1

如果你想将反应视为一个方程式而不是一个图表，你也可以使用 tikz 标记来做到这一点：

\documentclass{article}
\usepackage{amsmath, tikz}
\usetikzlibrary{decorations.pathreplacing, calc}
\newcommand{\tikzmathnode}[2]{\tikz[remember picture, baseline]{\node[inner sep=1pt, outer sep=0pt, anchor=base, minimum height=1em] (#1) {$\displaystyle #2$};}}
\newcommand{\redoxdraw}{
  \begin{tikzpicture}[overlay, remember picture]
    \draw[decoration = {brace, amplitude=.3em, raise=.1em}, decorate] (redox1.north east) -- (redox2.south east);
    \draw[-to, out=0, in=180] ([xshift=.8em] redox1.east) to ([xshift=2.5em] redox2.east);
    \draw[-to, out=0, in=180] ([xshift=.8em] redox2.east) to ([xshift=2.5em] redox1.east);
  \end{tikzpicture}
}
\newcommand{\redoxfirst}[1]{\tikzmathnode{redox1}{#1}\qquad}
\newcommand{\redoxsecond}[1]{\tikzmathnode{redox2}{#1}\qquad\redoxdraw}


\begin{document}
\begin{equation*}
  \begin{array}{rrrr}
    Cr: & \redoxfirst{3\downarrow} & 2Cr: & 6\downarrow\\[.3em]
     C: & \redoxsecond{2\uparrow}   & 3C: & 6\uparrow
  \end{array}
\end{equation*}
\end{document}

当然，您可以尝试调整间距或减少格式的硬编码。您还可以创建\redoxfirst并\redoxsecond接受一个可选参数来命名反应，以便在同一行中允许多个反应。

Answer 2

尝试\tikzmark：

\documentclass[a4paper]{article}
\usepackage{tikz}
\usepackage{tikz-cd}
\usetikzlibrary{decorations.pathreplacing}
\usetikzlibrary{calc,tikzmark}

\begin{document}
  \begin{tikzcd}
      Cr: & 3\downarrow  \tikzmark{bracebegin} \hspace{4pt} \arrow[rd] & \hspace{4pt} 2Cr: & 6\downarrow \\
      C: & 2\uparrow  \tikzmark{braceend} \hspace{4pt} \arrow[ru]   & \hspace{4pt} 3C: & 6\uparrow
  \end{tikzcd}
  \begin{tikzpicture}[overlay,remember picture]
  \draw[decorate,decoration={brace}] ( $ (pic cs:bracebegin) +(0, 9pt)  $ ) -- ( $ (pic cs:braceend) -(0, 4pt) $ );
  \end{tikzpicture}%
\end{document}

Answer 3

\documentclass[a4paper]{article}
\usepackage{tikz}
    \usetikzlibrary{decorations.pathreplacing}
\begin{document}
    \begin{tikzpicture}[node distance = 3cm]
        \node at (-1,1){Cr: 3};
        \draw[->](-0.5,1.1)--(-0.5,0.8);
        \node at (-1,-1){C: 2};
        \draw[->](-0.5,-1.1)--(-0.5,-0.8);
        \draw [->] (0,1) --(1,-1);
        \draw [->]  (0,-1) -- (1,1);
        \draw[decorate,decoration={brace}]  (-0.3,1.2) -- (-0.3,-1.2);
        \node at (1.7, 1.0){2 Cr: 6};
        \node at (1.7, -1.0){3Cr: 6};
        \draw[->](2.4,-1.1)--(2.4,-0.9);
        \draw[->](2.4,1.1)--(2.4,0.9);
    \end{tikzpicture}
\end{document}