Correct Answer: 18

Solution : The correct answer is 18 .

Elements with the electronic configuration [He]2s ² 2p ⁶ belong to Group 18, the noble gases that are colourless, odourless, diamagnetic, and non-toxic. Neon has an electron configuration of [He]2s ² 2p ⁶ . Noble gases have complete outer electron shells, making them stable and less likely to form chemical bonds. It is categorised as one of the noble gases, along with argon, krypton, xenon, and helium.