Final answer:
The main difference in the electronic structure of neon and argon is that argon has an additional electron shell compared to neon, which affects each element's chemical properties.
Step-by-step explanation:
The primary difference between the electronic structure of neon and argon relates to their electron configurations and the number of energy levels they occupy. By using spectroscopic notation, we know that neon has an electron configuration of [He]2s²2p¶, which means it has two electron shells and completes its outer shell with eight electrons (2 in the 2s and 6 in the 2p orbitals). In contrast, argon with the electron configuration of [Ne]3s²3p¶ has three electron shells and also completes its outer shell with eight electrons (2 in the 3s and 6 in the 3p orbitals). Hence, argon has an additional energy level with electrons compared to neon, which is fundamental to its chemistry.