Question

If K and L shells of an atom are full then what would be the total number of electrons in the atom? What is the valency of this element? Name the element.

Answer 1

Number of electrons in nth shell= 2n² 

Here n is the number of shell. 

As K and L shell is completely filled hence, there would be (2+8) = 10 electrons in atom. 

The element with atomic number 10 is inert gas neon (Ne) so the valency will be zero.