• In an emission spectrum, the limit of convergence at higher frequency corresponds to the first ionization energy.

• Trends in first 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 configurations.

• Solving problems using E=hv.

• Calculation of the value of the first ionization energy from spectral data which gives the wavelength or frequency of the convergence limit.

• Deduction of the group of an element from its successive ionization energy data.

• Explanation of the trends and discontinuities in first ionization energy across a period.

• The value of Planck’s constant (h) and 𝐸 = h𝑣 are given in the data booklet in sections 1 and 2.

• Use of the Rydberg formula is not expected in calculations of ionization energy.