Nuclear equations for the decay of radon-222 to lead-206
In any nuclear reactions the sum of the mass numbers $A_i$ (the sum of the indices on the top left) of the reagents and products is always the same. The same applies to nuclear charges $Z_i$ (indices in the lower left, which are often not indicated). Also, keep in mind the notation for metastable state:

$$
\begin{align}
\ce{^{222}_{86}Rn &amp;→ ^{218}_{84}Po + ^{4}_{2}He}\tag{a} \\
\ce{^{218}_{84}Po &amp;→ ^{214\mathrm{m}}_{82}Pb + ^{4}_{2}He}\tag{b} \\
\ce{^{214\mathrm{m}}_{82}Pb &amp;→ ^{214\mathrm{m}}_{83}Bi + ^{0}_{-1}e + γ}\tag{c} \\
\ce{^{214\mathrm{m}}_{83}Bi &amp;→ ^{214\mathrm{m}}_{84}Po + ^{0}_{-1}e + γ}\tag{d} \\
\ce{^{214\mathrm{m}}_{84}Po &amp;→ ^{214}_{85}At + ^{0}_{-1}e}\tag{e} \\
\ce{^{214}_{85}At &amp;→ ^{210\mathrm{m}}_{83}Bi + ^{4}_{2}He}\tag{f} \\
\ce{^{210\mathrm{m}}_{83}Bi &amp;→ ^{210\mathrm{m}}_{84}Po + ^{0}_{-1}e + γ}\tag{g} \\
\ce{^{210\mathrm{m}}_{84}Po &amp;→ ^{206}_{82}Pb + ^{4}_{2}He + γ}\tag{h} \\
\end{align}
$$