Plasmas are gases in which the molecules have been stripped of some or all of their electrons, to create positive ions.

ECONOMIST: Using a plasma torch to clean your teeth

The process is repeated to build up alternating layers of positive and negative ions on top of each other.

ECONOMIST: MONITOR

In an ultracapacitor, positively charged ions gather on the surface of the negatively charged electrode and negative ions on the surface of the positive electrode.

ECONOMIST: Electricity storage

These ions, like the hydrogen ions that are the heart of every acid, have a single positive charge.

ECONOMIST: Stomach turning