Neutral atoms balance protons and electrons

Steps:

• Gold has 79 protons in its nucleus.
• Neutrons (118) contribute to mass but not charge.
• In a neutral atom, electron number equals proton number for zero net charge.
• Thus, electrons total 79.

Why B is correct:

• Atomic number (79) defines protons; neutrality requires equal electrons per charge balance principle.

Why the others are wrong:

• A: 39 miscalculates half the protons, ignoring neutrality.
• C: 118 counts neutrons, which are uncharged.
• D: 197 sums protons and neutrons (mass number), not electrons.

Final answer: B