Answer: B. The nucleus contains protons and neutrons; only protons carry charge. So of 27 nuclear particles, 13 are protons and \(27 - 13 = 14\) are neutrons.
The ion is \(M^{x+}\) — a cation, so it has fewer electrons than protons (electrons = protons − charge). The exact value of \(x\) is not given, but any cation with 13 protons must have fewer than 13 electrons.
Option A says 13 neutrons — wrong (14 neutrons).
Option B says 13 protons and 10 electrons — protons correct, and 10 electrons gives \(x = +3\), which is consistent with a cation. ✓
Option C says 14 electrons — more electrons than protons would make it an anion, not \(M^{x+}\). Wrong.
Option D says 14 protons — wrong (13 protons).
13 protons identifies M as aluminium; B corresponds to \(\text{Al}^{3+}\).
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