Noble Gases' Stable Electron Configurations

Steps:

• Identify helium and neon as noble gases in Group 18.
• Recall noble gases have full valence electron shells: helium with 2 electrons, neon with 8.
• Understand full shells lead to low reactivity due to stability.
• Compare options to select the one matching full shell concept.

Why D is correct:

• According to the octet rule, atoms with completely filled valence shells achieve stability and do not form bonds easily, making helium and neon unreactive.

Why the others are wrong:

• A: Being gases relates to physical state, not chemical reactivity.
• B: Helium has only 2 outer electrons, not 8, so this is inaccurate.
• C: Equal protons and electrons define neutral atoms generally, not specific to unreactive noble gases.

Final answer: D