Which of the following elements has the highest ionization energy?

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

Answer: (C)

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 elements in the periodic table: Li and Na are in Group 1 (alkali metals), K is also in Group 1 but in a lower period, and Ne is a noble gas in Group 18 at the end of the second period.
3. Recall that noble gases 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 elements: Li, Na, and K are all alkali metals with relatively low ionization energies, and ionization energy decreases as you move down the group (Li > Na > K). Ne, being a noble gas, has a much higher ionization energy than any alkali metal.
5. Conclude that Ne (Neon) has the highest ionization energy among the given elements due to its full valence shell and position on the periodic table.