Which of the following atoms has the highest ionization energy?

• A. Na
• B. Mg
• C. K
• D. Ne

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. Generally, ionization energy 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 atoms in the periodic table: Na (Sodium) is in period 3, group 1; Mg (Magnesium) is in period 3, group 2; K (Potassium) is in period 4, group 1; Ne (Neon) is in period 2, group 18 (a noble gas).
3. Recall that noble gases like Ne 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 ionization energies based on their positions: Ne, being a noble gas in period 2, will have a higher ionization energy than Na, Mg, and K, which are metals and located in lower groups or periods.
5. Conclude that among the given options, Ne has the highest ionization energy due to its full valence shell and position in the periodic table.