Question

why he having 2 valence electron is not placed under the group along with be, mg and ca​

Answer 1

Answer:

helium have 2 valency

Explanation:

helium:

its outer most orbit is filled so helium is kept as Noble gas same like neon also have outer most orbit filled

I hope it helps

Answer 2

The reason for this is :-

He ( helium) have two electrons in its k shell ( first shell ) and k shell could only hold 2 electrons and hence its octet is filled completely . so its becomes a noble gas hence due to this reason it is placed in 18th group instead of keeping it in 2 nd group along with magnesium and calcium

hope it helps you

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