Parse the atomic number and ionization stage from representation of ion.

This function can take a number of formats for the ion name. As an example, all of the following representations of Fe 18, that is, an iron ion with 17 electrons removed and a total charge of +17, will return (26,18):

  1. 'Fe 18', 'fe 18' (atomic symbol and ionization stage)

  2. 'Fe 17+' (atomic symbol and charge state)

  3. 'Iron 18', 'iron 18' (element name and ionization stage)

  4. 'Fe XVIII', 'fe xviii' (atomic symbol and ionization stage in spectroscopic notation)

  5. '26 18' (atomic number and ionization stage)

  6. (26, 18) (tuple of any combination of the above)