Ionize or Ionise?

 In chemistry we have a verb to describe the process of producing ions, but how do you spell it?

Is it ionize? (rhymes with prize)

Or is it ionise? (rhymes with surprise)

The root of the word is Greek, so according to my school grammar teacher, the suffix should be "ize". The preferred IUPAC spelling appears to be ionize, and hence ionizing and ionization.

Similarly, we also have a verb to describe the process of producing atoms, also from a Greek root, so the preferred spelling should be atomize, not atomise. Hence we form the words atomizing and atomization.

I'm sure we'll continue to see the alternative spellings with an "s" rather than a "z" but they won't get you a Nobel Prise. Surprize!