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CAIE A-Level Chemistry 1.3.5 Explaining Electronic Configurations

Practise justifying electron arrangements through energy minimization and repulsion between electrons.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • fill lower-energy orbitals before higher-energy orbitals to obtain the ground state
  • place electrons singly in equal-energy orbitals before pairing to reduce inter-electron repulsion
  • pair at most two electrons with opposite spin in each orbital and explain exceptional 3d–4s arrangements carefully

1.3.5—Electronic configurations question 1

[Maximum number: 2]

The electronic configuration of a sulfur atom is 1s22s22p63s23p41 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{4}.

During the process of ionisation a sulfur atom loses an electron.

S( g)→S+(g)+e−ΔH=1000 kJ mol−1\mathrm{S}(\mathrm{~g}) \rightarrow \mathrm{S}^{+}(\mathrm{g})+\mathrm{e}^{-} \quad \Delta H=1000 \mathrm{~kJ} \mathrm{~mol}^{-1}

Identify the orbital from which this electron is removed. Explain your answer.
orbital
explanation

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