The presence of protons and neutrons at the center of the atom was suggested by:

In the Thomson's model of atom,which of the following statements are correct?
$(i)$ The mass of the atom is assumed to be uniformly distributed over the atom.
$(ii)$ The positive charge is assumed to be uniformly distributed over the atom.
$(iii)$ The electrons are uniformly distributed in the positively charged sphere.
$(iv)$ The electrons attract each other to stabilize the atom.

How did Rutherford prove that positively charged particles are present in the nucleus of an atom?

Match the names of the scientists given in column $A$ with their contributions towards the understanding of the atomic structure as given in column $B$.

Column $A$	Column $B$
$(a)$ Ernest Rutherford	$(i)$ Indivisibility of atoms
$(b)$ $J$.$J$. Thomson	$(ii)$ Stationary orbits
$(c)$ Dalton	$(iii)$ Concept of nucleus
$(d)$ Neils Bohr	$(iv)$ Discovery of electrons
$(e)$ James Chadwick	$(v)$ Atomic number
$(f)$ $E$. Goldstein	$(vi)$ Neutron
$(g)$ Mosley	$(vii)$ Canal rays

Which of the following figures do not represent Bohr's model of an atom correctly?

$(a)$ Describe the main features of Bohr's model of an atom. Draw a neat and labelled diagram of energy levels.
$(b)$ Which of the following pairs are isotopes and which are isobars?
$(i)$ $_{26}^{58} A, _{28}^{58} B$
$(ii)$ $_{35}^{79} X, _{35}^{80} Y$
$(c)$ Elements $A$ and $B$ have atomic numbers $18$ and $16$ respectively. Which of these two would be more reactive and why?