How many electrons are in the outer electron shell of group 1 elements?

• A. 1
• B. 2
• C. 3
• D. 4

Answer: (A)

Group 1 elements have one valence electron in their outermost shell. Their electron configurations end with s1, such as lithium with 2s1, sodium with 3s1, potassium with 4s1, and so on. That single outer electron defines the number of electrons in the outer shell. So the outermost shell contains exactly one electron. This is why these elements tend to lose that one electron to reach a stable noble-gas configuration, giving them a +1 charge. Other numbers would correspond to different groups (two for group 2, three for group 13, four for group 14), but not for group 1.