Structure of the Atom from NCERT Class IX Science traces how our picture of the atom developed, from the discovery of electrons and protons to Thomson's, Rutherford's and Bohr's models and the neutron. It then explains how electrons are arranged in shells, valency, atomic number and mass number, and isotopes and isobars. These ideas form the foundation for the periodic table and chemical bonding in later classes. These free MCQ practice tests check both concepts and simple applications, helping you prepare for class tests and school exams. Every test is timed, scored instantly and comes with a complete answer review.