The electronic configuration of the atom having max difference in first and 2nd ionization energies.

Question

$(a)\;1S^2,2S^2,2P^1 \\(b)\; 1S^2,2S^2,2P^6,3S^1 \\ (c)\;1S^2,2S^2,2P^3 \\ (d)\;1S^2,2S^2,2P^3,2S^2$