Respuesta :
Helium is a noble gas with a stable electronic configuration. It differs from other elements in group 18 as it has two valence electrons, while the rest of them has 8 valence electrons. Thus, option a is correct.
What are the properties of helium?
Helium is a noble gas or inert gas placed in group 18 of the periodic table with atomic number 2. It is an s-block element as its valence electron lies in the s- subshell. Its configuration is,
He (2) ⇒ 1s²
The other elements of the group include neon, krypton, radon, xenon, and argon which have eight valence electrons in their outermost shell of the atom that completes their octet and makes them stable.
Therefore, option a. the helium differs from the other noble gas of the same group as it has two valence electrons while others have eight valence electrons.
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