The number of electrons in an element $X$ is $15$ and the number of neutrons is $16$. Which of the following is the correct representation of the element?

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?

State whether the following statement is true or false:
The relative number and kinds of atoms are varying in a given compound.

An atom with $3$ protons and $4$ neutrons will have a valency of:

State three rules suggested by Bohr and Bury for the distribution of electrons into different orbits (shells) of an atom.

Dalton's atomic theory successfully explained which of the following laws?
$(i)$ Law of conservation of mass
$(ii)$ Law of constant composition
$(iii)$ Law of radioactivity
$(iv)$ Law of multiple proportion