Which of the following ion formation is always exothermic ?
Correct answer: A. Uni-negative
- A. Uni-negative
- B. Uni-positive
- C. Di-negative
- D. Di-positive
Explanation
Formation of a uni-negative ion involves adding one electron, and the first electron affinity of an atom is generally exothermic because the incoming electron is attracted to the positive nucleus. Formation of a positive ion requires ionisation energy and is endothermic, while adding a second electron is usually endothermic because it enters an already negative ion. The likely mistake is choosing c by thinking that adding electrons always releases energy, although electron-electron repulsion makes second-electron addition unfavorable.
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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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