Which of the following elements has the highest ionization energy?

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

Answer: (A)

Verified step by step guidance

1. Recall 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: Li (Lithium), Na (Sodium), and K (Potassium) are all in Group 1 (alkali metals), with K being the lowest period, then Na, then Li; Ne (Neon) is a noble gas in Group 18, at the end of the second period.
3. Understand that noble gases like Neon have very high ionization energies because they have a full valence shell, making them very stable and less willing to lose electrons.
4. Compare the trends: Since ionization energy increases across a period and Ne is to the right of Li, Na, and K, and also higher up in the periodic table compared to Na and K, Ne will have the highest ionization energy among the options.
5. Conclude that Neon (Ne) has the highest ionization energy because it is a noble gas with a full valence shell and is located at the top right of the periodic table among the given elements.