ion

UK/ˈaɪən/US/ˈaɪ.ɑn/

nounB2+Occasional — familiar, but not everyday · #11,322 of 15,258mostly written

Other forms: ions

An ion is an atom that has gained or lost an electron. A negative ion, ion channel, ionised gas.

Because it is charged, it moves in an electric field, which is where the name comes from — the Greek means going. Nerves work by ions crossing the cell membrane, and salt dissolves into them, which is why salty water conducts.

ion — EliseEtc / vectorised from Ionic bonding.png · CC BY-SA 3.0

Definitions of ion

1nounionAn atom that has gained or lost an electron.B2+
“When salt dissolves in water, it splits into sodium and chloride ions.”

ion is a particle.

Where it comes from

Greek ion means going, coined by William Whewell in 1834 for particles that travel towards an electrode.

Ancient Greek
εἶμι
English, today
ion

Built from

εἶμι · Ancient Greek — I go

From Ancient Greek εἶμι. From the ending of anion and cation, which in turn is from Ancient Greek ἰόν (“going”), neuter present participle of εἶμι (“I go”). coined by William Whewell in 1834 for Michael Faraday, who introduced it later that year.

Etymology from Wiktionary, CC BY-SA

Practised in Chemistry & Elements

Practise this word

ion in the wild

Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore.
Ion channel
An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion.
Ion thruster
An ion thruster creates a cloud of positive ions from a neutral gas by ionizing it to extract some electrons from its atoms.
Ion thruster
Li-ion batteries have enabled portable consumer electronics, laptop computers, cellular phones, and electric cars.
Lithium-ion battery
Progress has been made in the development and manufacturing of safer lithium-ion batteries.
Lithium-ion battery

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From Wikipedia, CC BY-SA 4.0. These sentences were written by other people about their own subjects; they are here to show the word at work, not as anybody’s opinion.

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ion