There are quite a number of YouTube videos featuring explosions. One that caught my eye recently features the reactions (explosions) of the heavier alkali metals, Rb and Cs. The “experiments” could be legitimate, but with television you never know. Then there is the lab demo of the reaction betwen bromine and potassium. My personal favorite is the combustion of Magnesium in CO2 (Dry Ice).
Some years back I decided that I would treat my class to a demo on the reduction of CO2 with magnesium. I had already done the Mg/CO2 demo before, but I learned in Bassam Shakhashiri’s book on demonstrations that the addition of a smidgen of potassium chlorate to the magnesium would assure that the Mg would ignite properly. Make no mistake, Shakhashiri is much beloved in the chem educator field and rightfully so. His demonstrations are legendary.
I was a little uncertain of the wisdom of using potassium chlorate, so I decided it would be prudent to try out Shakhashiri’s modification in advance. One evening in my research lab I chiseled out a small indentation in a block of dry ice and added a Mg ribbon “fuse”, Mg turnings, and the recommended mass of potassium chlorate. I ignited the ribbon and held the second dry ice block in front of me, ready to place it on the burning Mg. As the burn reached the chlorate there was a blinding flash and a loud BLAM! When I opened my eyes I saw that the papers on the benchtop were ablaze and that the block of dry ice I was holding prevented burning Mg frags from lodging in my clothing. The air was cloudy with MgO dust, my ears were ringing, and expletives were flying out of my mouth.
Better that it happened in private than in front of 65 students. The students’ burns would heal. But, more importantly, the damage to my reputation would have been horrific.
A few years later at an ACS meeting, in the mens room at the convention center in San Diego, I was standing at the urinal when who should take the urinal right next to me? Bassam Shakhashiri. I pondered the opportunity this might present. Suddenly the moment passed and we both finished our business and went on with our day. One of us nearly left with a wet shoe.
Lamentations on Chemistry 
Skivved Teflon tape is *the* thing to wrap around pipe threads before screwing together plumbing. If the threads are (freshly cut) aluminum alloy, the joint offers an explosive counterargument. Teflon-covered stir bar in an LAH reduction, no problem. Add dry LAH to the (moving) stir bar (no solvent), problem. Big AlF3 heat of formation.
Magnesium is particulary hazardous for its low boiling point (compare with aluminum). Reducing metal oxides with aluminum (e.g., thermite) is a pussycat. Substitute magnesium and get a four-foot flare of beyond white hot burning metal vapor. This is a bad thing (certainly for stoichiometry).
Uncle Al suggested a daisy cutter bomb shell witha central big bursting charge, surface det cord to peel it like an orange, and a couple of tons of AlMe3 as fill. Drop it at night from a cargo plane with big white parachutes, strobes, and sirens. When everybody is looking up, WHAMMO! The military has no sense of theatre.
The first video is bull. How could Cesium which has less atoms make a bigger boom than Potassium that has many-many more.
Mitch
Hi Mitch, I suppose the format of the program seems a bit too “Hollywood”, so it is conceivable that the explosions were contrived. I assume you’re suggesting that if equal weights of metals were used, and thus fewer moles were allowed to contact the water as you go down the group, there should be fewer moles of H2 evolved and thus a smaller bang. The rate of energy release could be related to the rate of dispersion of the metal, which could be related to the rate of temperature increase of the bulk metal . Hard to say without doingsome experiments yourself. Guess we could order some Cs from Strem and do the deed.