The first model of an atom was given by

Write three observations of Rutherford's alpha particles scattering experiment.

In response to a question,a student stated that in an atom,the number of protons is greater than the number of neutrons,which in turn is greater than the number of electrons. Do you agree with the statement? Justify your answer.

Atomic models have been improved over the years. Arrange the following atomic models in their chronological order:
$(i)$ Rutherford's atomic model
$(ii)$ Thomson's atomic model
$(iii)$ Bohr's atomic model

$(i)$ Write the postulates of the Bohr model of an atom.
$(ii)$ Draw a sketch of the Bohr model of an atom with atomic number $15$.

$A, B$ and $C$ are three metals with atomic numbers $4, 11$ and $13$ respectively. Arrange the metals in the increasing order of their valency.