P primer

In the Cambrian Period, 500 million years ago, the armored set ruled the seas. Soft-bodied animals secreted a mineral paste that hardened into protective shells of immense strength and deco beauty, some shaped like rams’ heads or eagles’ wings, others like champagne flutes studded with dagger-sharp spines.

But by the Devonian Period some 70 million years later, most of these brachiopods, briopods and related well-shelled mariners had gone extinct, victims of theft and their own extravagant ways.

“If you heat phosphorus under different conditions, different temperatures, different pressures, strange things start to happen,” Andrea Sella, a professor of inorganic chemistry at University College London, said. “You get red fibrous forms, metallic black forms, purple forms.” You can also stack up layers of phosphorus atoms and then pull them apart into ultrathin and flexible sheets called phosphorenes, all with the goal of controlling the flow of electrons and light particles on which technology depends. “We’ve only scratched the surface of what this element can do,” Dr. Sella said.