Question

select all that apply
which statements about hydrogen and helium are true?

the electron dot diagram for helium consists of the symbol he and one dot.
helium contains two electrons in its lone energy level.
the outer energy level of helium is not full.
the outer energy level of hydrogen is not full.
the electron dot diagram for hydrogen consists of the symbol h and no dots.
hydrogen contains one electron in its lone energy level.

Explanation:

• Helium:
• Helium has an atomic number of \(2\). Its electron configuration is \(1s^{2}\). The first (and only for helium) energy level (\(n = 1\)) can hold a maximum of \(2\) electrons. So, helium has two electrons in its lone energy level.
• For the electron - dot diagram (Lewis dot structure), we represent the valence electrons. Helium has \(2\) valence electrons. The electron - dot diagram for helium is \(:\text{He}:\) (two dots), not one dot.
• Since the first energy level (\(n=1\)) of helium is filled (holds \(2\) electrons which is the maximum for \(n = 1\)), the statement “The outer energy level of helium is not full” is false.
• Hydrogen:
• Hydrogen has an atomic number of \(1\). Its electron configuration is \(1s^{1}\). So, hydrogen has one electron in its lone energy level.
• The first energy level (\(n = 1\)) can hold a maximum of \(2\) electrons. Since hydrogen has only \(1\) electron in the \(n = 1\) level, the outer energy level of hydrogen is not full.
• For the electron - dot diagram of hydrogen, we represent its \(1\) valence electron. The electron - dot diagram for hydrogen is \(\text{H}\cdot\) (one dot), not no dots.

Answer:

• Helium contains two electrons in its lone energy level.
• The outer energy level of hydrogen is not full.
• Hydrogen contains one electron in its lone energy level.