A research chemist studies a gaseous element R and determines the energies required…
CHEMISTRY · Multi-part · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends
Problem
A research chemist studies a gaseous element R and determines the energies required to remove successive electrons. The cumulative ionization energies are plotted below as a function of the number of electrons removed. The plot is described verbally:
• The first point at 580 kJ mol⁻¹ corresponds to removal of one electron.
• The second point, 1820 kJ mol⁻¹, lies 1240 kJ mol⁻¹ above the first.
• The third point, 2750 kJ mol⁻¹, lies 930 kJ mol⁻¹ above the second.
• The fourth point, 11 800 kJ mol⁻¹, lies 9050 kJ mol⁻¹ above the third.
• The fifth point, 15 200 kJ mol⁻¹, lies 3400 kJ mol⁻¹ above the fourth.
• The sixth point, 18 900 kJ mol⁻¹, lies 3700 kJ mol⁻¹ above the fifth.
Assume R is in the first three periods of the periodic table.
(a) Using the information provided, calculate the incremental (individual) fourth ionization energy, IE₄, of element R.
(b) Identify the most significant jump in individual ionization energy values for R and state between which two successive electrons the jump occurs.
(c) From your answer to part (b), determine the total number of valence electrons in a neutral atom of R. Explain your reasoning.
(d) When reacted with oxygen, R forms an oxide whose empirical formula is R₂O₃. Use your answers from parts (b) and (c) to justify why this formula is consistent with the electron configuration of R.
(e) The chemist claims that R is aluminum. Evaluate this claim, citing evidence from the ionization-energy data, periodic trends, and the empirical formula of the oxide.