Which of the following elements has the highest ionization energy?
Correct answer: D. Ar
- A. Na
- B. Si
- C. Cl
- D. Ar
Explanation
The correct answer is Argon (Ar). In the periodic table, ionization energy generally increases across a period from left to right. This is because the effective nuclear charge increases, causing the electrons to be held more tightly by the nucleus. Among the given options, Ar is a noble gas with a full outer electron shell, resulting in the highest ionization energy as it is energetically stable and resists losing an electron. Sodium (Na), being in Group 1, has the lowest ionization energy as it readily loses an electron to achieve stability. Silicon (Si) has higher ionization energy than Na but lower than Cl and Ar. Chlorine (Cl) has high ionization energy, but not as high as Ar, due to its need to gain one electron to achieve a noble gas configuration.
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About Periodic Properties and Trends
Periodic properties arise from electron configuration and effective nuclear charge, producing trends in atomic and ionic radius, ionization energy, electron affinity, electronegativity, metallic character and reactivity. Comparisons run across periods and down groups, with attention to common exceptions. The topic also relates these trends to the behavior of s-block and p-block elements.
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