Can chemical bonds affect the rate of electron capture?
Chemical bonds can affect the rate of electron capture, although the effect is small.
Beryllium-7 is the lightest atom that decays by electron capture. The rate of electron capture of bonded atoms differs from that of nonbonded atoms by 0.9 %. In other atoms, the effect is much less than 0.9 %.
During electron capture, the nucleus captures an electron from the K or L shell.
This relatively large effect in beryllium occurs because beryllium is a small atom. Its valence electrons are in the L shell and close to the nucleus.
In most other atoms that undergo electron capture, the valence electrons are much farther from the nucleus. The effect is much less than in beryllium.