He was a genius among middle school biology teachers, and also a ham. He didn’t just take joy in science, he took glee. He loved shoving cages of frogs up next to each other so that they’d display for us. He made a pageant of the periodic table.
One if his favorite groups of elements was Group 1, the alkali metals. His method was dropping a chunk of one in water, producing a sudden whoosh of flame. “Don’t try this at home kids!” he’d admonish. He was right too. It would have been a good way to burn down the garage. “Come here for all your science needs.”
The alkali metals are lithium, sodium, potassium, rubidium, caesium, and francium. These are soft bright metals, with boiling points that lower as they move up the periodic table. They also catch fire, at the very least, if dunked in water.
Francium is radioactive and rare, the second rarest element on earth (after astatine). Perhaps one ounce exists at a time in the entire crust, with a new supply constantly being born out of actinium-227 and swiftly decaying to astatine, radium, and radon. As ninth-graders, we never saw Francium.
Cesium is not used in grade school science classes partly because most of its isotopes are radioactive. Also, it does not merely catch fire when it touches water, it explodes. Its melting point is 83 degree F., which makes it a silvery-gold liquid in a warm room. It is mined in the ore pollucite, mostly in Canada, and its radioactive isotopes are recovered from nuclear waste.
Rubidium is used in fireworks, to make purple starbursts. Like the other alkali metals, it will rapidly oxidize in air and burn more quickly than anyone can imagine in water. It has one stable isotope, but 28% of naturally occurring rubidium is radioactive, with a half-life much longer than the age of the universe.
Potassium can be used in a classroom, with care and judgment. Our teacher used special tongs to remove a bit from mineral oil, where it is stored to prevent an oxide covering that can cause explosive flame if scratched. He dropped it in a beaker of water, and enjoyed our reaction. The chemical reaction is (in English) two atoms of solid potassium plus two liquid water molecules react to produce a molecule of hydrogen and some dissolved potassium hydroxide. It happens very fast, and the hydrogen generally catches fire.
Sodium, as in common table salt, is an alkali metal too. Like the other alkali metals, it is too reactive to be found uncombined on earth. Lithium is the lightest alkali metal. It is a scientific mystery, because there seems to be too little around in the universe to match our cosmology.
Hydrogen is nominally an alkali metal, from its position in the periodic table, but does not behave like one, though I believe our teacher proved it burns readily in air.
Mr. Smith worked summers analyzing canned food, to support his family and his teaching habit. He bought plenty of toys for his classes and himself, and he must have started many scientists and engineers on their way. He knew his stuff.
