The correct answer to the question is option C. Helium atoms have 2 valence electrons, while atoms of the other elements in the group all have 8 valence electrons.
Group 18 of the periodic table are known as the noble gas family. Their outermost shell is completely filled.
Members of the group 18 includes:
1. Helium (He)
2. Neon (Ne)
3. Argon (Ar)
4. Krypton (Kr)
5. Xenon (Xe)
6. Radon (Rn)
Among this group, only Helium (He) has a valence electron of 2. Other members of the group has a valence electron of 8.
Helium is part of the group 18 because its outermost shell is completely filled by its 2 electrons.
Therefore, option C gives the right answer to the question as helium only have 2 valence electrons while other members of the group has 8 valence electrons.
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