Radon 222 decay chain.

\usetikzlibrary{fit,math,positioning}
\newcommand{\nnnkl}[3]{${}_{#3}^{#2}\textrm{#1}$}
\begin{tikzpicture}[
    nucleus/.style={scale=1,thick,draw,rectangle,minimum height=1ex,minimum width=10ex,align=flush center,fill=black!90,rounded corners},
    decay/.style={thick,->,align=flush center,color=orange!80,font=\small},
    bango/.style={sloped,below left=-0.5ex and -3ex}
    ]
    \node[nucleus] (Ra226) {\nnnkl{Ra}{224}{} \\1620 y};
    \node[nucleus,below=5ex of Ra226] (Rn222) {\nnnkl{Rn}{222}{} \\ 3.82 d};
    \node[nucleus,below=5ex of Rn222] (Po218) {\nnnkl{Po}{218}{} \\ 3.1 m};
    \node[nucleus,below=5ex of Po218] (Pb214) {\nnnkl{Pb}{214}{} \\ 27 m};
    \node[nucleus,above right=-1.5ex and 6ex of Pb214] (Bi214){\nnnkl{Bi}{214}{} \\ 20 m};
    \node[nucleus,above right=-1.5ex and 6ex of Bi214] (Po214) {\nnnkl{Po}{214}{} \\ 160$\mu$s};
    \node[nucleus,below=5ex of Po214] (Pb210) {\nnnkl{Pb}{210}{} \\ 22 y};
    \node[nucleus,above right=-1.5ex and 6ex  of Pb210] (Bi210){\nnnkl{Bi}{210}{} \\ 5 d};
    \node[nucleus,above right=-1.5ex and 6ex of Bi210] (Po210) {\nnnkl{Po}{210}{} \\ 138 d};
    \node[nucleus,below=5ex of Po210] (Pb216) {\nnnkl{Pb}{206}{} \\ stable};
    \draw[decay] (Ra226.south) -- node [right] { $\alpha$ \\ 4870keV}  (Rn222.north);
    \draw[decay] (Rn222.south) -- node [right] { $\alpha$ \\ 5590keV}  (Po218.north);
    \draw[decay] (Po218.south) -- node [right] { $\alpha$ \\ 6114keV}  (Pb214.north);
    \draw[decay] (Pb214.east)  -- node [bango] { $\beta$  \\ 1024keV} (Bi214.west);
    \draw[decay] (Bi214.east)  -- node [bango] { $\beta$  \\ 3272keV}  (Po214.west);
    \draw[decay] (Po214.south) -- node [right] { $\alpha$ \\ 7833keV}  (Pb210.north);
    \draw[decay] (Pb210.east)  -- node [bango] { $\beta$  \\ 63.5keV}  (Bi210.west);
    \draw[decay] (Bi210.east)  -- node [bango] { $\alpha$ \\ 1162keV}  (Po210.west);
    \draw[decay] (Po210.south) -- node [right] { $\alpha$ \\ 5407keV}  (Pb216.north);
\end{tikzpicture}