Which of the following elements has the largest first ionization energy?

• A. Na (Sodium)
• B. Li (Lithium)
• C. K (Potassium)
• D. Ne (Neon)

Answer: (D)

Verified step by step guidance

1. Understand that the first ionization energy is the energy required to remove one electron from a neutral atom in the gaseous state.
2. Recall that ionization energy generally increases across a period (left to right) in the periodic table because the effective nuclear charge increases, pulling electrons closer and making them harder to remove.
3. Recall that ionization energy generally decreases down a group (top to bottom) because the outer electrons are farther from the nucleus and are shielded by inner electrons, making them easier to remove.
4. Identify the positions of the elements: Li, Na, and K are all alkali metals in Group 1, with Li at the top, Na in the middle, and K at the bottom of the group, while Ne (Neon) is a noble gas at the end of the second period.
5. Conclude that Neon has the largest first ionization energy among the given elements because it is a noble gas with a full valence shell and is located to the right of Li, Na, and K on the periodic table, resulting in a much higher effective nuclear charge and a more stable electron configuration.