Which one of the following is the correct sequence according to atomic weights?
Correct answer: B. Co > Ni > Fe
- A. Fe>Co> Ni
- B. Co > Ni > Fe
- C. Ni> Co> Fe
- D. Co >Fe>Ni
Explanation
The atomic weights are Fe = 55.85 g mol-1, Co = 58.93 g mol-1 and Ni = 58.69 g mol-1. Therefore, Co > Ni > Fe, even though cobalt and nickel occur in an unusual order compared with their atomic numbers. Students may choose a by assuming the order of atomic numbers and atomic weights must be identical.
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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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