Which of the following best explains why sodium is more reactive than magnesium?

• A. Sodium is a transition metal, while magnesium is an alkali metal.
• B. Sodium has a higher atomic number than magnesium, which increases its reactivity.
• C. Sodium has a lower ionization energy than magnesium, making it easier to lose its outer electron.
• D. Sodium has more valence electrons than magnesium, leading to greater reactivity.

Answer: (C)

Verified step by step guidance

1. Understand the position of sodium and magnesium in the periodic table: Sodium (Na) is an alkali metal in Group 1, and magnesium (Mg) is an alkaline earth metal in Group 2.
2. Recall that reactivity in metals, especially in Groups 1 and 2, is largely influenced by how easily the atom can lose its outermost electron(s), which relates to ionization energy.
3. Compare the ionization energies of sodium and magnesium: Sodium has a lower first ionization energy than magnesium, meaning it requires less energy to remove its outer electron.
4. Recognize that sodium has only one valence electron, while magnesium has two; losing one electron is easier than losing two, so sodium tends to be more reactive.
5. Conclude that the best explanation for sodium's higher reactivity is that it has a lower ionization energy, making it easier to lose its outer electron compared to magnesium.