Find the number of electrons,protons,and neutrons possessed by the alpha particles $\left({ }_{2}^{4} He ^{2+}\right)$ used in the gold leaf experiment.

Which of the following statements are true for an element?
$(i)$ Atomic number $=$ number of protons $+$ number of electrons
$(ii)$ Mass number $=$ number of protons $+$ number of neutrons
$(iii)$ Atomic mass $=$ number of protons $=$ number of neutrons
$(iv)$ Atomic number $=$ number of protons $=$ number of electrons

Rutherford's $\alpha$-particle scattering experiment showed that:
$(i)$ electrons have negative charge
$(ii)$ the mass and positive charge of the atom is concentrated in the nucleus
$(iii)$ neutron exists in the nucleus
$(iv)$ most of the space in the atom is empty
Which of the above statements are correct?

Name the particles which determine the mass of an atom.

Dalton's atomic theory successfully explained:
$(i)$ Law of conservation of mass
$(ii)$ Law of constant composition
$(iii)$ Law of radioactivity
$(iv)$ Law of multiple proportions

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.