The number of maximum electrons in N shell is

What is the maximum number of electrons in the M-Shell ?

What is the maximum number of electrons that can occupy the first shell of an atom ?

The number of electrons and neutrons in an element is 18 and 20 respectively. Its mass number is

Number of electrons present in the species H₂⁺, He, H and O₂⁺ respectively are :

The number of neutrons in the nucleus of plutonium nuclide ( ₉₄Pu²⁴²) is :