GK QUESTION#3298
Consider the following statements about electron configuration and groups in the periodic table:
1. Elements of Group 2 have two electrons in their outermost shell.
2. Halogens belong to Group 17 and contain five electrons in the valence shell.
3. Noble gases have completely filled outer shells and are generally inert.
Which of the above statements is/are correct?
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Answer
A. Only 1 and 3
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Explanation
Group 2 atoms have an outer ns² configuration. Halogens in Group 17 have seven valence electrons, not five. The familiar noble gases have closed outer shells and are generally unreactive, although some form compounds. Thus statements 1 and 3 are correct.