What were the names of the atomic bombs that America decided not to drop?

Answer 1

There were none, we only had the two. We had the materials to make a few more but they were not assembled and ready to use at the time.

A third unnamed MK-III Plutonium bomb core (counting the Gadget's core that was used in the Trinity Test) was shipped from Los Alamos a few days after the August 9 bombing of Nagasaki and arrived in San Francisco on August 18 where Colonel Tibbetts waited in a B-29 to transport it across the Pacific to Tinian for eventual use on Japan in late August. However as the Japanese had indicated their willingness to surrender on August 14, president Truman made the decision to have it returned to Los Alamos instead of using it.

The production schedule and facilities allowed for the manufacturing and dropping of as many as 23 atomic bombs on Japan in 1945, limited mostly by the capacity of the Hanford reactors to produce enough plutonium for 3 bombs per month.

1. August - 1 MK-I Uranium gun bomb (Little Boy) and 2 MK-III Plutonium implosion bombs (Fatman & unnamed)
2. September - 3 MK-III Plutonium implosion bombs (canceled), Hanford had probably already produced the Plutonium for 1 or 2 of these bombs by the middle of August but Los Alamos had probably not manufactured cores from it before Truman canceled further atomic bombings
3. October - 3 MK-III Plutonium implosion bombs (canceled)
4. November - 7 MK-III Mod 1 Plutonium/Uranium composite core implosion bombs (canceled)
5. December - 7 MK-III Mod 1 Plutonium/Uranium composite core implosion bombs (canceled)

It has been confirmed that more than 1 Plutonium bomb core existed at Los Alamos at the time of the Trinity Test (July 16) but whether that was just the one for Fatman or included the final August core or maybe even some of the September cores cannot be determined from unclassified documents.

There may have been unassembled casings and kits of the nonnuclear components of up to a dozen MK-III bombs already waiting on Tinian in August for their Plutonium cores. There had been several dozen nonnuclear practice "pumpkin" bombs having the same dimensions and weight as the MK-III atomic bomb on Tinian and the 509th had dropped several on Japan through July and early August to practice for the actual atomic bombings (as well as getting the Japanese used to seeing missions of just 3 B-29s dropping only one bomb that demolished roughly one city block so that they might not consider such flights as serious threats and scramble fighters against the actual early atomic bombing missions).