An element in Group 17 typically has how many electrons in its outer shell?

• A. 1
• B. 7
• C. 5
• D. 3

Answer: (B)

Group 17 elements have seven electrons in their outer shell. The number of valence electrons in main-group elements corresponds to the group, and halogens sit with seven valence electrons, ending their outer shell in p5 configurations (like F ending in 2p5, Cl in 3p5, etc.). This is why they’re highly reactive: they’re just one electron short of a full octet, so they commonly gain one electron or share electrons to complete their outer shell. The other numbers would place you in different groups with different valence electron counts, not Group 17. So seven electrons in the outer shell is the correct idea.