Wikipedia:Reference desk/Archives/Science/2022 February 9

= February 9 =

Which was used first in nuclear bombs? Radium or Plutonium?
I couldn't find any specific information on nuclear bombs that answered this question.


 * "The world's first nuclear explosion occurred on July 16, 1945, when a plutonium implosion device was tested ..." Clarityfiend (talk) 07:48, 9 February 2022 (UTC)
 * I don't think radium has ever been used to create a nuclear bomb. Clarityfiend (talk) 07:50, 9 February 2022 (UTC)
 * Radium is not particularly fissile, which means it does not undergo a spontaneous fission reaction. Not all radioactive materials do so.  Generally speaking, most fissile elements are isotopes of actinides with odd mass numbers.  Radium is not an actinide, and has only 5 isotopes that have a halflife of more than a few seconds; of those only two have halflives measured in years; radium-228 and radium-226, both of which are even mass number. -- Jayron 32 12:10, 9 February 2022 (UTC)
 * The OP was probably thinking of "uradium". Clarityfiend (talk) 22:10, 9 February 2022 (UTC)

See Trinity (nuclear test). The Manhattan Project created two bomb designs: a uranium gun-type bomb ("Little Boy"), and a more complicated plutonium implosion type bomb ("Fat Man"). Little Boy was simple enough that they were sure it would work on the first try, but Fat Man had to be tested first, just in case. So the first three explosions were 1) Trinity, a test explosion in New Mexico of the Fat Man design, mentioned above as the first nuclear explosion; 2) Little Boy, dropped on Hiroshima and therefore the first atom bomb actually dropped in a war; and 3) Fat Man, a second copy of the implosion design, dropped on Nagasaki. I'm sure Wikipedia's articles cover this stuff in detail, but a very thorough history is the 1987 book The Making of the Atomic Bomb. 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 09:42, 13 February 2022 (UTC)

Explosion/burning in chemical equation
In chemical equation are there any symbols / special characters to indicate that the reaction produces an explosion, vigorous burning or similar hazard? Googling only suggested that "gas explosion can be simplified as an one-step, exothermic chemical reaction: CH4 + 2O2 → CO2 + 2H2O + 886.2kJ/mol". Thanks. 212.180.235.46 (talk) 12:16, 9 February 2022 (UTC)
 * I've only ever seen that denoted using $$\Delta H_{\text {reaction}}^\ominus$$. Professional chemists will do a hazard/risk assessment (similar to HACCP) before they attempt any lab-work since having a career in chemistry means avoiding blowing up oneself or colleagues. In my industrial lab it was, for example, prohibited to do anything for the first time on a scale greater than 0.1 mol so that even if the hazard were underestimated the resulting exotherm would be unlikely to do much damage. Mike Turnbull (talk) 12:44, 9 February 2022 (UTC)
 * The $$\Delta H$$ of a reaction only tells the difference between the starting and ending points, not how fast it got there. There are many reactions which are highly exothermic (rusting, for example), but which have very slow kinetics; if a massive amount of energy is released, but it does so over years, than the reaction is not described as explosive.  Even if less energy is released, if the energy is released in fractions of a second, and if the energy does pressure volume work, only THEN could it be described as an explosion.  To answer the OP's question, no, there is not any particular way to indicate "explosiveness" in a chemical equation.  -- Jayron 32 13:09, 9 February 2022 (UTC)
 * Thanks,, that reminds me that that the thermite reaction converting the rust back to iron can also be fast and furious. Also worth mentioning for the OP is that in many lab reactions the real hazard is any flammable solvent, which is usually present in much larger amounts than the reagent and if set alight can give many times more than the reaction's exotherm. Mike Turnbull (talk) 13:38, 9 February 2022 (UTC)
 * Just a side note, taking the oxygen out of rust is still endothermic in that half of the Thermite reaction. It's the putting the oxygen on aluminum in the other part which is so exothermic.  And yes, the reaction is vigorous because the kinetics are rather rapid.  -- Jayron 32 14:10, 9 February 2022 (UTC)

Tigraan Click here for my talk page ("private" contact) 17:58, 9 February 2022 (UTC)
 * In addition to the considerations of kinetics, "explosion" is not really a scientific term, so there is no real demarcation between burning and exploding. There is a scientifically-meaningful distinction between deflagration and detonation depending on whether the flame propagates slower or quicker than sound in the medium (the latter allows for a shock wave to form, among other things).
 * There are no rigorous rules, but if a single molecule of a material in the solid or liquid state releases multiple gas molecules during the reaction (e.g. TNT), it indicates the reaction is potentially explosive, due to the sudden increase in atmospheric pressure. 51.155.110.141 (talk) 22:59, 10 February 2022 (UTC)