Conception and Patent for the Atomic Bomb
On September 12, 1932, within seven months of the discovery of the neutron, and more than six years before the splitting of the atom, Leo Szilard conceived of the possibility of a release of atomic energy via a neutron-based chain reaction, and also realized that a bomb could be built.
On July 4, 1934 Leo Szilard filed a patent application for the atomic bomb. In his application, Szilard described not only the basic concept of using neutron induced chain reactions to create explosions, but also the concept of the critical mass. The patent was awarded to him - making Leo Szilard the legally recognized inventor of the atomic bomb.
Szilard attempted to keep the patent secret (so as not to tip off Germany)
by gifting it to the British War Office. They initially rejected, then
later accepted a few months later in February 1936.