Radon 220 decay chain.

\newcommand{\nkllrnttz}[2]{${}^{#2}{\text{#1}}$}
\begin{tikzpicture}[
    nucleus/.style={scale=1,thick,draw,rectangle,minimum height=1ex,minimum width=10ex,align=flush center,fill=gray!20,rounded corners},
    decay/.style={thick,->,align=flush center,color=blue!80,font=\small},
    bangolab/.style={sloped,below left=-0.5ex and -3ex},
    bangonuc/.style={nucleus,above right=-1.5ex and 8ex}
    ]
    \node[nucleus] (Th228) {\nkllrnttz{Th}{228} \\ 1.91 yr};
    \node[nucleus,below=5ex of Th228] (Ra224) {\nkllrnttz{Ra}{224} \\3.66 d};
    \node[nucleus,below=5ex of Ra224] (Rn220) {\nkllrnttz{Rn}{220} \\55.6 s};
    \node[nucleus,below=5ex of Rn220] (Po216) {\nkllrnttz{Po}{216} \\0.145 ns};
    \node[nucleus,below=5ex of Po216] (Pb212) {\nkllrnttz{Pb}{212} \\10.6 h};
    \node[nucleus,above right=-1.5ex and 8ex of Pb212] (Bi212) {\nkllrnttz{Bi}{212} \\ 60.5 m};
    \node[nucleus,below=5ex of Bi212] (Tl208) {\nkllrnttz{Tl}{208} \\ 3.05 m};
    \node[nucleus,above right=-1.5ex and 8ex of Bi212] (Po212) {\nkllrnttz{Po}{212} \\ 60.5 m};
    \node[nucleus,below=5ex of Po212] (Pb208) {\nkllrnttz{Pb}{208} \\ 3.05 m};
    \draw[decay] (Th228.south) -- node [right] { $\alpha$ \\ 5520keV}     (Ra224.north);
    \draw[decay] (Ra224.south) -- node [right] { $\alpha$ \\ 5789keV}  (Rn220.north);
    \draw[decay] (Rn220.south) -- node [right] { $\alpha$ \\ 6404keV}  (Po216.north);
    \draw[decay] (Po216.south) -- node [right] { $\alpha$ \\ 6904keV}  (Pb212.north);
    \draw[decay] (Po212.south) -- node [right] { $\alpha$ \\ 8955keV}   (Pb208.north);
    \draw[decay] (Bi212.south) -- node [right] { $\alpha$ \\ 6208keV}  (Tl208.north);
    \draw[decay] (Pb212.east) -- node [bangolab]  { $\beta$  \\ 570keV}  (Bi212.west);
    \draw[decay] (Bi212.east) -- node [bangolab]  { $\beta$  \\ 2252keV}  (Po212.west);
    \draw[decay] (Tl208.east) -- node [bangolab]  { $\beta$  \\ 4999keV}  (Pb208.west);
\end{tikzpicture}