Which of the following elements has the highest ionization energy?

• A. Ne (Neon)
• B. Al (Aluminum)
• C. Na (Sodium)
• D. Mg (Magnesium)

Answer: (A)

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), Magnesium (Mg), Aluminum (Al), and Neon (Ne). All are in the same period (Period 3), with Neon being a noble gas at the far right.
3. Recall the trend that ionization energy increases as you move from left to right across a period because the effective nuclear charge increases, pulling electrons closer and making them harder to remove.
4. Compare the elements based on their position: Sodium is far left, followed by Magnesium, then Aluminum, and Neon is at the far right of Period 3.
5. Conclude that Neon, being a noble gas with a full valence shell, has the highest ionization energy among the listed elements due to its stable electron configuration and strong effective nuclear charge.