The electron configurations of four elements are listed - VCE - SSCE Chemistry - Question 13 - 2004 - Paper 1

To find which electron configuration corresponds to the element least likely to act as a reductant, we need to analyze the valence electron configurations. A reductant is typically an element that can easily lose electrons.

• Option A: 1s² 2s² 2p⁶ 3s² 3p¹

  • This configuration indicates that the element has three valence electrons (2 from 3s and 1 from 3p) and can act as a reductant.

• Option B: 1s² 2s² 2p⁶ 3s² 3p⁵

  • This configuration shows five valence electrons in the 3rd shell, indicating that the element is likely a non-metal (specifically a halogen) and is less likely to act as a reductant since it tends to gain electrons.

• Option C: 1s² 2s² 2p⁶ 3s² 3d¹⁰ 4s²

  • This element has an outer configuration of 4s², making it less likely to lose electrons compared to those in lower energy levels.

• Option D: 1s² 2s² 2p⁶ 3s² 3p³ 4d¹⁰ 4s²

  • Similar to option C, this element has a filled d-subshell, which typically is less reactive in terms of losing electrons.

Thus, among these options, Option B (1s² 2s² 2p⁶ 3s² 3p⁵) is the configuration of the element least likely to act as a reductant.