● In an emission spectrum, the limit of convergence at higher frequency corresponds to the fi rst
ionization energy.
● Trends in fi rst ionization energy across periods account for the existence of main energy levels and
sub-levels in atoms.
● Successive ionization energy data for an element give information that shows relations to electron
confi gurations.

● Solving problems using E = h.
Guidance
The value of Planck’s constant and E = h are given in the IB data booklet in sections 1 and 2.
● Calculation of the value of the fi rst ionization energy from spectral data which gives the
wavelength or frequency of the convergence limit.
Guidance
Use of the Rydberg formula is not expected in calculations of ionization energy.
● Deduction of the group of an element from its successive ionization energy data.
● Explanation of the trends and discontinuities in data on fi rst ionization energy across a period.