Chemistry – Atoms, elements and compounds - Isotopes | e-Consult
Atoms, elements and compounds - Isotopes (1 questions)
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The magnesium atom has an atomic number of 12, so it has 12 protons and 12 neutrons. The mass number is the sum of protons and neutrons. Therefore, the mass number of the magnesium atom is 12. A magnesium ion with a charge of 2 means it has lost two electrons. This means it has 12 protons and 10 neutrons. The mass number is 12 + 10 = 22. The symbol for the magnesium ion is 22Mg2+.