Single correct option
An element has the electronic configuration 2, 8, 7. It belongs to which group of the modern periodic table?
- A. Group 7
- B. Group 17
- C. Group 15
- D. Group 16
Show answer and solution
Answer: (B) Group 17
The element has 17 electrons (chlorine) with 7 valence electrons. For main-group elements the group number is 10 plus the number of valence electrons for groups 13 to 18, so 7 valence electrons correspond to group 17, the halogens. Group 7 is a transition-metal group and a wrong reading of the old numbering.
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