Question

Is it possible to have an element with atomic number 1.5 placed between hydrogen and helium?

Answer 1

No it can't be possible because atomic numbers of elements are always n whole numbers.

Answer 2

" the atomic number of any of the element should only be a whole number "
example -
1. Boron : It's atomic number is 5
2. Argon : it's atomic number is 18 

∴ it is impossible to have an element with a atomic number 1.5 which is to be placed in between Hydrogen and Helium