Which of the following best explains why Na(s) is more reactive with water than Mg(s)?

• A. Na is less soluble in water than Mg, leading to greater reactivity.
• B. Na has a higher atomic mass than Mg, which increases its reactivity.
• C. Na forms a covalent bond with water, while Mg does not.
• D. Na has a lower ionization energy than Mg, making it easier to lose an electron.

Answer: (D)

Verified step by step guidance

1. Understand that reactivity of metals with water is largely influenced by how easily the metal atoms lose electrons to form positive ions.
2. Recall that ionization energy is the energy required to remove an electron from an atom; lower ionization energy means it is easier for the atom to lose an electron.
3. Compare the ionization energies of sodium (Na) and magnesium (Mg): sodium has a lower first ionization energy than magnesium because it has only one electron in its outer shell, while magnesium has two.
4. Recognize that because sodium loses its outer electron more easily, it reacts more readily with water to form Na⁺ ions and hydrogen gas.
5. Conclude that the statement 'Na has a lower ionization energy than Mg, making it easier to lose an electron' best explains why sodium is more reactive with water than magnesium.