In 1920, Ernest Rutherford speculated on the possible existence and properties of the neutron in his second Bakerian Lecture, London, on “The Nuclear Constitution of Atoms.” He considered isotopes for which “…provided the resultant nuclear charge is the same, a number of possible stable modes of combination of the different units which make up a complex nucleus may be possible.” Later he said, “Under some conditions, however, it may be possible for an electron to combine much more closely with the H nucleus, forming a kind of neutral doublet. Such an atom would have very novel properties. Its external field would be practically zero, except very close to the nucleus…” In 1932, Chadwick discovered the neutron.«