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

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

The number of maximum electrons in N shell is

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

What is the mass number of an element, the atom of which contains two protons, two neutrons and two electrons?

The atoms, in which the number of protons is same but the number of neutrons is different, are known as –