Question

helium is in group 18 of the periodic table. how is helium different from the other elements in this group? (1 point) helium atoms have 2 valence electrons, while atoms of the other elements in the group all have 8 valence electrons. helium atoms have valence electrons in the first energy level, while atoms of the other elements in the group have valence electrons in the second energy level. helium atoms have a full outer energy level, while atoms of the other elements in the group do not have a full outer energy level. helium atoms have 2 electrons, while atoms of the other elements in the group all have 18 electrons.

Explanation:

1. Analyze the first option: Group 18 elements (noble gases) have full valence shells. Helium has 2 valence electrons (filling the first energy level), and other noble gases (like Ne, Ar) have 8 valence electrons (filling their outer energy levels). This is correct.
2. Analyze the second option: Other group 18 elements have valence electrons in different outer energy levels (e.g., Ne in second, Ar in third), not all in the second. So this is incorrect.
3. Analyze the third option: All group 18 elements have full outer energy levels. So this is incorrect.
4. Analyze the fourth option: Other group 18 elements have different electron counts (e.g., Ne has 10, Ar has 18), not all 18. So this is incorrect.

Answer:

A. Helium atoms have 2 valence electrons, while atoms of the other elements in the group all have 8 valence electrons.