Final answer:
The true statement about the magnesium ion is b) 'It has lost two electrons to become a cation'. Magnesium, with an atomic number of 12, forms a magnesium ion (Mg2+) by losing two electrons, resulting in a cation with a charge of 2+.
Step-by-step explanation:
The question is asking about the properties of the magnesium ion. Statement b) 'It has lost two electrons to become a cation' is true. Magnesium has an atomic number of 12, meaning it has 12 protons. A neutral magnesium atom also has 12 electrons. However, when it forms an ion, it tends to lose two electrons to achieve a stable electron configuration, akin to the nearest noble gas, which in this case is neon. This loss of electrons results in a positively charged ion, known as a cation, making Mg2+ a magnesium ion with a charge of 2+.
There seems to be a common misconception represented in option a) 'It has 10 protons and 12 electrons' and option d) 'It has 12 protons and 10 electrons', which are both incorrect regarding the magnesium ion. The correct electron count for a magnesium ion is 10, as it has lost 2 electrons, but the proton count in the nucleus remains the same at 12. Option c) 'It has gained two electrons to become an anion' is not applicable to magnesium as it does not gain electrons to form ions.
The formation of ions is a key concept in chemistry, particularly when discussing ionic compounds such as the one formed between magnesium and nitrogen. Magnesium forms a cation with a charge of 2+ (Mg2+), while nitrogen, being a nonmetal, gains electrons to form an anion with a charge of 3- (N3-).