An electronic configuration that has maximum difference between II and III ionization potential is:

Ionization potential (or Enthalpy) increases successively ($IE_1 < IE_2 < IE_3 < \dots$). A sudden large jump in ionization energy occurs when an electron is removed from a stable noble gas configuration (core shell) after the valence electrons have been removed.

1. Analyze the jump between $IE_2$ and $IE_3$: This implies that the 2nd electron is removed easily (valence shell), but the 3rd electron is removed from a stable core. This characteristic belongs to an element with 2 valence electrons ($ns^2$ configuration).
2. Evaluate Option B ($1s^2 2s^2 2p^6 3s^2$): This is Magnesium (Mg, Group 2). Removal of 1st electron ($3s^2 \rightarrow 3s^1$): $IE_1$ (low). Removal of 2nd electron ($3s^1 \rightarrow 2p^6$): $IE_2$ (relatively low, empties valence shell). Removal of 3rd electron ($2p^6 \rightarrow 2p^5$): $IE_3$ (Very High). This involves breaking the stable octet of the Neon core ($[Ne]$). Therefore, the difference between $IE_3$ and $IE_2$ is maximum.
3. Check other options: Option A ($3s^1$): Alkali metal. Max difference is between $IE_1$ and $IE_2$. Option C ($2p^6$): Noble gas. High IEs generally, but no specific 'valence-to-core' jump between 2 and 3.

• Option D ($2p^5$): Halogen. Valence electrons are removed in steps, no core break between 2 and 3.