Protons determined by atomic number Steps:

• Atomic number defines the number of protons: F has 9, Na has 11.
• Subtract: 11 protons (Na) - 9 protons (F) = 2 more protons in Na atom.
• Neutrons require mass number (nucleons) minus protons, but description is ambiguous.
• Na+ ion forms by losing 1 electron from neutral Na (11 electrons → 10 electrons); neutral F has 9 electrons.

Why A is correct:

• Atomic number equals proton number by definition, so Na (11) has exactly 2 more protons than F (9).

Why the others are wrong:

• B: Not enough information; "nucle number 19 23" is ambiguous and does not clearly specify mass numbers for neutron calculation.
• C: Na+ has 10 electrons, while neutral F atom has 9 electrons.

Final answer: A