Electron count comparison for ammonium ion and neutral atoms

Steps:

• Ammonium ion (NH4+) consists of nitrogen (7 electrons) and 4 hydrogens (4 electrons total), yielding 11 electrons; the +1 charge removes 1 electron, leaving 10.
• Neutral atoms have electrons equal to their atomic numbers: Mg (12), Na (11), Ne (10), O (8).
• Compare: only Ne matches the 10 electrons of NH4+.
• Confirm via noble gas configuration: NH4+ achieves neon-like stability with 10 electrons.

Why C is correct:

• Neon (atomic number 10) has exactly 10 electrons, matching NH4+'s electron count per ion formation rules.

Why the others are wrong:

• A. Mg has 12 electrons, exceeding NH4+ by 2.
• B. Na has 11 electrons, exceeding NH4+ by 1.
• D. O has 8 electrons, fewer than NH4+ by 2.

Final answer: C