Which atom has the highest first ionization energy?

• A. Na
• B. Ne
• C. Mg
• D. Al

Answer: (B)

Verified step by step guidance

1. Understand that the first ionization energy is the energy required to remove one electron from a neutral atom in the gaseous state.
2. Recall that ionization energy generally increases across a period (left to right) in the periodic table because the nuclear charge increases, pulling electrons closer and making them harder to remove.
3. Identify the elements given: Sodium (Na), Neon (Ne), Magnesium (Mg), and Aluminum (Al), and note their positions in the periodic table. Neon is a noble gas at the end of the period, while the others are metals earlier in the same period.
4. Recognize that noble gases like Neon have a full valence shell, which makes their electrons more tightly bound and results in a higher first ionization energy compared to metals in the same period.
5. Conclude that Neon has the highest first ionization energy among the given atoms because it has a full outer shell and a higher effective nuclear charge experienced by its valence electrons.