Which of the following elements has the highest ionization energy?

• A. Na (sodium)
• B. Li (lithium)
• C. Al (aluminum)
• D. F (fluorine)

Answer: (D)

Verified step by step guidance

1. Understand that ionization energy is the energy required to remove an electron from a gaseous atom or ion. It generally increases across a period (left to right) on the periodic table and decreases down a group (top to bottom).
2. Identify the positions of the given elements on the periodic table: Sodium (Na) and Lithium (Li) are in Group 1 (alkali metals), Aluminum (Al) is in Group 13, and Fluorine (F) is in Group 17 (halogens).
3. Compare the elements based on their group and period: Fluorine is to the right and above the others, meaning it has a smaller atomic radius and a stronger effective nuclear charge, which usually leads to higher ionization energy.
4. Recall that elements in Group 17 have higher ionization energies than those in Groups 1 and 13 because they are closer to completing their valence shell and hold their electrons more tightly.
5. Conclude that among the listed elements, Fluorine has the highest ionization energy due to its position on the periodic table and its strong attraction for its valence electrons.