Two of most unique elements on the periodic table are hydrogen and helium. What makes them so unique and removed from the other groups on the periodic table?

Question

a
Unlike all other elements, hydrogen and helium are gases
b
Unlike all other elements, hydrogen and helium are not considered metals
c
Unlike all other elements, hydrogen and helium only have a maximum of 2 valence electrons
d
Unlike all other elements, hydrogen and helium have very limited properties

Answer 1

The most accurate statement explaining what makes hydrogen and helium unique compared to other groups on the periodic table is:

c Unlike all other elements, hydrogen and helium only have a maximum of 2 valence electrons.

Hydrogen has one electron and can hold a maximum of 2 in its first energy level when it forms covalent bonds, while helium has two electrons in its outer shell, fulfilling the duet rule. Most other elements have more complex electron configurations and can have more than 2 valence electrons.

While options a and b have some truth to them, they are not comprehensive enough in capturing the uniqueness of both elements compared to all others on the periodic table. Option d is too vague.