1. The President of the United States: Franklin Delano Roosevelt; Democrat of NY; elected 1932, 36, 40, 44, died 4/45; succeeded by VP Harry S. Truman; Democrat, former senator from MO.
2. The Secretary of War: Henry L. Stimson; Republican, former Cabinet officer in Republican administration.
3. The Director of the ``Manhattan Engineer District'': Leslie L. Groves; career officer in US Army Corps of Engineers; previously supervised construction of Pentagon building.
4. The Director of the Los Alamos laboratory: J. Robert Oppenheimer; Professor of Theoretical Physics at both UC Berkeley and CalTech; precocious; left-wing politics.

Name each of them, and give a brief description of the background of each (using only the space provided).

A radioactive isotope of polonium  ₈₄²⁰⁹Po was used in the ``initiator'' for the atomic bomb.

1. What is the number of protons N_p, neutrons N_n, and electrons N_e in a neutral atom of this isotope?
   

   N_p = 84
   

   N_n = 209 - 84 = 125
   

   N_e = N_p = 84

2. The isotope has a half-life of about 100 years, and emits an alpha (a) particle. When it decays it turns into a different element.

   What are the numerical values of the Atomic Number and Mass Number of this new element?
   

   Atomic Number Z = 84 - 2 = 82
   

   Mass Number A = 209 - 4 = 205

1. Explain why a heavy nucleus, such as uranium, is susceptible to fission while a middle-weight nucleus, such as iron or copper, is not.: Because the nuclei into which uranium splits are more-strongly bound, the mass of the products is less than the mass of the uranium. Thus, according to E = mc² energy is released when uranium splits. Energy would be required to split iron.
2. Who made the experimental discovery of nuclear fission? Where was the discovery made?: Hahn and Strassmann in Dahlem/Berlin, Germany in late 1938
3. Who provided the realization that the process really was nuclear fission? Where was that done?: Meitner and Frisch in Sweden and Denmark in late 1938-early '39.