Question

The noble gas having only two electrons in its valence shell is ______.

Options

• Ar

• Ne

• He

• Kr

Answer 1

He

Explanation:

Helium (He) has an atomic number of 2, meaning it has 2 electrons. These two electrons completely fill its first and only energy level (the K shell), satisfying the stable duplet rule. While all other noble gases like Argon, Neon, and Krypton achieve chemical stability with eight valence electrons (the octet rule), Helium is uniquely stable with just two.