Comparing electrons and neutrons in ions using common isotopes

Steps:

• Determine atomic number Z (protons) and most abundant mass number A for each element.
• Calculate neutrons n = A - Z (unchanged in ions).
• Calculate electrons e: e = Z + charge magnitude for anions, e = Z - charge for cations.
• Compare e and n for equality.

Why A is correct:

• For F⁻, Z=9, A=19, n=10, e=9+1=10; electrons equal neutrons by definition of ion charge adjusting electron count to match common isotope neutrons.

Why the others are wrong:

• B: For P³⁻, Z=15, A=31, n=16, e=15+3=18; 18 ≠ 16.
• C: For Na⁺, Z=11, A=23, n=12, e=11-1=10; 10 ≠ 12.
• D: Not enough information (option incomplete).

Final answer: A