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

and reactivity

Answer 2

Correct answer is actually A.

Answer 3

A. Unlike all other elements, hydrogen and helium are gases

What is special about hydrogen and helium?
Hydrogen and helium are the lightest elements in the periodic table having mass number 1 and 2 respectively. They both exist in the form of gases at room temperature. Both Hydrogen and helium are the two most common elements in the universe. Hydrogen make up about 75% of all matter present in the universe. Hydrogen belongs to the metal group but it is not metal but a gas.

So we can conclude that option A is the right answer for the given question.