The object of their attention is the single electron in the outermost electron shell of a potassium atom.

Add three potassium atoms, and it becomes a low- temperature superconductor.

Add three more potassium atoms, and it becomes an insulator again!

A potassium atom is thus much more likely to lose the "extra" electron than to gain one; however, the alkalide ions, K, are known.

In the usual process, sodium atoms in the surface layer of the glass are replaced by potassium atoms.

The potassium atoms, being slightly larger, make for a tighter fit among the glass molecules, compressing them.

"With four potassium atoms added, for example, it was about 9 percent wider and 3 percent shorter."

Each potassium atom gave about six-tenths of the charge of an electron.

The potassium atoms switched places with the sodium atoms at the surface, making the glass stronger.

Why did the glass become stronger, and why did the potassium atoms take the places of the sodium atoms?