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

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

Answer: (C)

Verified step by step guidance

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