1834

Ion

• Michael Faraday knew
• electrolosis carried some kind of particle
• to one electrode or the another.
• His friend William Whewell
• suggested naming this kind of particle “ion,”
• Greek for the verb meaning going.

Charged particles

• Normally, in an atom, each proton,
• which has a positive electric charge,
• is exactly balanced by an electron,
• which has a negative electric charge.
• If an atom has more electrons
• than protons, it has a net negative charge.
• It’s attracted to the anode of a battery,
• so Faraday called this an “anion.”
• If an atom has fewer electrons
• than protons, it has a net positive charge.
• It’s attracted to the cathode of a battery,
• so Faraday called this a “cation.”
• During electrolysis, a substance
• is dissolved by a solvent, which produces either
• anions attracted to the positive anode
• or cations attracted to the negative cathode.

Faraday cup

• Transient and fragile particles
• and any extra electrons
• are detected by a Faraday cup
• as they exit the target end
• of a particle accelerator.
• These devices are finely tuned
• to show single elementary electric charges
• each about 1.602
• times 10 to the minus 19 coulombs.
• Faraday didn’t invent the Faraday cup,
• but he explained that electrolysis moves ions
• and observed that ions of the same charge
• repel each other.

Going

• I have the spring and clockwork
• of a four-wheeled toy that I wind up,
• set on the floor, and let go—
• instant joy, simple as going.
• But when a good friend dies,
• it’s hard not to refuse
• the pleasures of this world—
• too fragile, too temporary.