Question

Both helium and beryllium have two electrons in the valence shells. Helium is a nobble gas where as beryllium is a metal, justify ​

Answer 1

This is because:

1. The valance electrons of He are present in the first shell which is the K shell. Its maximum capacity is 2 electrons (using 2n sq, n = 1). Therefore it has already achieved a duplet which makes it stable.

2. On the other hand, for Be, only 2 electrons are present in a shell that has capacity for 8. It needs to achieve an octet to be stable. Since it has 2 extra electrons which it will donate to achieve stability and form a cation, it is classified as a metal.

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