Question

valence electrons 1 quick check
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 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 valence electrons, while atoms of the other elements in the group all have 8 valence electrons.
• helium atoms have 2 electrons, while atoms of the other elements in the group all have 18 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.

Explanation:

1. Analyze Option 1: All noble gases (group 18) have full outer energy levels. So this is incorrect.
2. Analyze Option 2: Helium has 2 valence electrons (its outer shell is full with 2 as it's in the first energy level), while other noble gases (like Ne, Ar) have 8 valence electrons (since their outer shells are in higher energy levels that can hold 8 to be full). This is correct.
3. Analyze Option 3: Other group 18 elements don't have 18 electrons. For example, Neon has 10, Argon has 18 but others like Krypton have 36. So this is incorrect.
4. Analyze Option 4: Other group 18 elements have valence electrons in their outermost energy level (which is not the second for all, e.g., Argon's valence electrons are in the third energy level). So this is incorrect.

Answer:

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