  The $\beta$ and double-$\beta$ decay channels, which are not accompanied by
excitation of the electron shells, are suppressed due to the nonorthogonality
of the electron wave functions of the parent and daughter atoms. The effect is
sensitive to the contribution of the outer electron shells. Since valence
electrons participate in chemical bonding and collectivize in metals, the decay
rates of the unstable nuclides are modified when they are embedded in a host
material. Core electrons are less affected by the environment, and their
overlap amplitudes are more stable. The suppression effect is estimated for $
\beta^- $ decay of $^{87}$Kr, electron capture in $^{163}$Ho, and $2\beta^-$
decays of $^{76}$Ge, $^{100}$Mo, $^{130}$Te, and $^{136}$Xe. The overlap
amplitude of the electron shells enters the relationship between the half-life
of neutrinoless $2\beta$ decay and the effective electron neutrino Majorana
mass.
