\begin{tikzpicture}[node distance=0.7cm,->,>=stealth',shorten >=0pt, scale=1]
  \tikzstyle{abstract}=[rectangle, draw=white, rounded corners, fill=white,
    text centered, anchor=north]
  \def\nodeshift{0.8cm}
  \newcommand{\Dsize}{\scriptsize\bf\sf}
  \newcommand{\Esize}{\tiny\sf}

  \Dsize
  \definecolor{red}{RGB}{221,42,43}
  \definecolor{green}{RGB}{132,184,24}
  \definecolor{blue}{RGB}{0,72,112}
  \definecolor{orange}{RGB}{192,128,64}
  \definecolor{gray}{RGB}{107,108,110}
  \colorlet{black}{gray}

  \node (Uranium) [abstract] {\textcolor{gray}{$^\text{232}$Th}};
  \node (AuxNode01) [text width=1cm, below=of Uranium] {};
  \node (Bismuth) [abstract, right=of AuxNode01] {$^\text{212}$Bi};
  \node (AuxNode02) [below=of Bismuth,yshift=\nodeshift] {{\Esize(\unit[60.5]{min})}};
  \node (Thallium) [abstract, below=of AuxNode02] {\textcolor{blue}{\textbf{$^\text{208}$Tl}}};
  \node (AuxNode03) [below=of Thallium,yshift=\nodeshift] {{\Esize(\unit[3.1]{min})}};
  \node (Polonium) [abstract, right=of Uranium, xshift=2.5cm,yshift=-0.5cm] {\textcolor{red}{\textbf{$^\text{212}$Po}}};
  \node (AuxNode04) [below=of Polonium,yshift=\nodeshift] {{\Esize\textcolor{red}{\textbf{(\unit[300]{ns})}}}};
  \node (Lead) [abstract, below=of AuxNode04] {$^\text{208}$Pb};
  \node (AuxNode05) [below=of Lead,yshift=\nodeshift] {{\Esize(stable)}};

  \draw[thick, dashed, gray] (Uranium.east) -- ([yshift=0.5cm]Bismuth.west);
  \draw[thick] (AuxNode02.south) -- (Thallium.north);
  \draw[thick,blue] (Bismuth.east) -- (Polonium.west);
  \draw[thick,red] (AuxNode04.south) -- (Lead.north);
  \draw[thick] (Thallium.east) -- (Lead.west);

  \path (1,-2.0) node[anchor=base west] {{\Esize 36\%}};
  \path (4.1,-1.5) node[anchor=base west,red] {{\Dsize $\boldsymbol{\alpha}$}};
  \path (2.8,-1.2) node[anchor=base west,blue] {{\Dsize $\boldsymbol{\beta}$}};

\end{tikzpicture}%

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