Magnesium and iron are metallic elements. How does a mole of magnesium compare with a mole of iron?

• A. A mole of magnesium contains fewer atoms than a mole of iron.
• B. A mole of magnesium contains more atoms than a mole of iron.
• C. A mole of magnesium has a greater mass than a mole of iron.
• D. A mole of magnesium contains the same number of atoms as a mole of iron.

Answer: (D)

Verified step by step guidance

1. Recall the definition of a mole: one mole of any substance contains Avogadro's number of particles, which is approximately \$6.022 \times 10^{23}$ atoms or molecules.
2. Understand that this means one mole of magnesium atoms contains exactly the same number of atoms as one mole of iron atoms, regardless of the element.
3. Recognize that while the number of atoms is the same, the mass of one mole of magnesium and one mole of iron will differ because their atomic masses are different.
4. Note that magnesium has an atomic mass of about 24.3 g/mol, and iron has an atomic mass of about 55.8 g/mol, so one mole of iron weighs more than one mole of magnesium.
5. Conclude that the correct comparison is that a mole of magnesium contains the same number of atoms as a mole of iron, but their masses are different.