Sodium-22 undergoes electron capture according to the following nuclear equation:
#""_-1^0"e" + _11^22"Na" -> _10^22"Ne"#
Notice that the electron capture of Na-22 results in nuclear transmutation; the inner-orbital electron is captured by the nucleus, the result being the formation of a neutron from the combination of said electron with a proton from the nucleus.
This process will reduce the atomic number by 1 (#11->10#), but leave the atomic mass unchanged.
You will sometimes see the electron capture of Na-22 being described as a positron emission. The nuclear equation for that process is
#""_11^22"Na" -> _10^22"Ne" + beta^(+) + nu_e#, where
#beta^(+)# - a positron - the antiparticle of the electron (same mass, opposite charge);
#nu_e# - a neutrino;
Electron capture can be viewed as the equivalent process to positron decay, since both processes result in the same nuclear transmutation - the formation of #""_10^22"Ne"#.