Which of the following elements has the greatest ionization energy?

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

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) and decreases down a group (top to bottom) in the periodic table.
2. Identify the positions of the given elements: Li (Lithium), Na (Sodium), and K (Potassium) are all in Group 1 (alkali metals) but in different periods, with Li in period 2, Na in period 3, and K in period 4.
3. Recognize that as you move down Group 1 from Li to K, the ionization energy decreases because the outermost electron is farther from the nucleus and more shielded by inner electrons, making it easier to remove.
4. Note that Ne (Neon) is a noble gas located at the end of period 2, with a full valence shell, which makes it very stable and gives it a much higher ionization energy compared to alkali metals.
5. Conclude that among the elements listed, Ne (Neon) has the greatest ionization energy due to its full valence shell and position on the periodic table, which results in a stronger attraction between the nucleus and its electrons.