Question

Both helium and beryllium have two electron in the valence shells. Helium is noble gas where as beryllium is a metal. Justify

Answer 1

Helium have full filled s orbital ofvits principal quantom no.(1s^2)that,s it counts into nobelbgas but in case of beryllium at.no.4 it has full filled s orbital but not complete of its quantum no.(its 2p is empty)1s^22s^2.hence it doesnot count in nobel gas

Answer 2

Even though both helium and beryllium have 2 electrons in their valence shell Helium is considered to be a noble gas whereas beryllium is a metal because helium has a complete electronic configuration whereas beryllium has incomplete electronic configuration

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