What forms from the decay of potassium-37?

Potassium - 37 decays by positron emission to form the
unstable argon - 37. And then another positron emission finally yields chlorine -37
which is stable.

K-37 + e- -->
Ar-37

Ar-37 + e- -->
Cl-37

Positron emission is a process where a proton is
converted to a neutron, a positron and a neutrino. The emission of a positron can be
considered to be the same as electron capture as a positron is the anti-matter form of
an electron. A positron emission reduces the atomic number of the resultant atom by one
though the atomic mass remains the same.