Question

Why can there only be 2 electrons in the first shell?

Answer 1

according to the Bohr-Bury scheme there can only be 2n^2 atoms in the shell

here n=1

so there can only be 2x 1^2=2x1=2 atoms in the first shell or the K-Shell

Answer 2

According to Bohr’s model
In K-shell i.e. first shell there is two electrons only.
In L shell i.e. second shell there is eight electrons only .