The questions are on the ionisation energy test. Take it under real conditions before reading the mark scheme.
Quick answer: An atomic orbital is a region around a nucleus that holds at most two electrons, and orbitals come as s, p and d types. This mark scheme gives the model answers and the marks for the 8 questions of the Chemistry 11-12 test on ionisation energy, from configurations of nickel to chromium, with the equivalent answers to accept.
Marks are given for method and for the final answer with its unit. Allow follow-through where an earlier error is carried forward correctly. Explanations must name the factor involved, not just state the trend.
Level: Chemistry grades 11-12 (A Level · IB · Class 11-12) · Curriculum: A Level 3.1.1, IB S1.3
Question 1 Configurations of nickel (2 marks)
a. [Ar] 3d⁸ 4s².b. The 4s electrons are lost first: [Ar] 3d⁸.
Marking: 1 mark each; accept 1s² 2s² 2p⁶ 3s² 3p⁶ in place of [Ar].
Question 2 Defining ionisation energy (2 marks)
It is the energy needed to remove one electron from each atom in one mole of gaseous aluminium atoms. Al(g) → Al⁺(g) + e⁻.Marking: 1 mark for mole and gaseous atoms; 1 mark for the correct equation with states.
Question 3 Reading the graph (4 marks)
a. The jump follows electron 2, so Z is in group 2.b. Z²⁺.
c. The third electron comes from an inner shell, closer to the nucleus and less shielded, so it is held far more strongly and needs much more energy.
Marking: (a) 1; (b) 1; (c) 1 for inner shell, 1 for closer or less shielded.
Question 4 Neon and argon (3 marks)
Argon’s outer electron is in the third shell and neon’s in the second. The third-shell electron is further from the nucleus and is shielded by more inner electrons. These effects outweigh the larger nuclear charge, so less energy is needed.Marking: 1 for the shell, 1 for distance, 1 for shielding.
Question 5 Energy for lithium (2 marks)
E = 0.0500 mol × 520 kJ mol⁻¹ = 26.0 kJ.Marking: 1 for the multiplication; 1 for the correct answer with unit.
Question 6 Carbon in boxes (2 marks)
Carbon has 2 unpaired electrons, in separate 2p orbitals with parallel spins, following Hund’s rule.Marking: 1 for two; 1 for Hund’s rule.
Question 7 Phosphorus and sulfur (2 marks)
In sulfur, one 3p orbital holds a pair of electrons. The repulsion between the pair makes one of them easier to remove than the unpaired 3p electrons of phosphorus.Marking: 1 for paired electrons in one orbital; 1 for repulsion.
Question 8 Chromium (3 marks)
Chromium is [Ar] 3d⁵ 4s¹. With one electron in each 3d orbital and one in 4s, there are six unpaired electrons and less repulsion than with a paired 4s², and the 3d and 4s energies are close, so this arrangement has lower energy.Marking: 1 for the configuration; 1 for half-filled 3d; 1 for lower energy or lower repulsion.
