Understanding Magnesium: Atomic Number, Mass Number, and Charge

Atomic number:

The atoms, isotopes, and ions of Magnesium have the same atomic number. The atomic number of an element is the number of protons found in the nucleus of an atom. It determines the identity of the element and its place on the periodic table. For Magnesium, the atomic number is 12.

Isotopes:

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This results in isotopes having different mass numbers. Despite the difference in mass number, the atomic number remains constant for all isotopes of an element.

Ions:

An ion is an atom or molecule that has gained or lost electrons, resulting in a positive or negative charge. In the case of Magnesium ions, they may have a charge of +2 due to losing two electrons to form a stable electron configuration. However, the atomic number, which is based on the number of protons, remains unchanged.

Therefore, the correct answer is option A: Atomic number. Despite variations in mass number and charge, the atomic number of Magnesium stays consistent across all its atoms, isotopes, and ions.