State whether the following statement is true or false:
One atomic mass unit is a mass unit equal to exactly one-twelfth $(1/12)$ the mass of one atom of carbon-$12$.

Mention the postulates of Niels Bohr put forth to overcome the objections raised against Rutherford's atomic model.

$(a)$ What are canal rays? Who discovered them? What is the charge and mass of canal rays?
$(b)$ How are the canal rays different from electrons in terms of charge and mass?

Identify the most stable atom from the following. Also give a reason for your answer.
$Na_{11}^{23}, Cl_{17}^{35}, Al_{13}^{27}, Ar_{18}^{40}$

Show diagrammatically the electron distributions in a sodium atom and a sodium ion and also give their atomic number.

Rutherford designed an experiment to determine the structure of an atom. Answer the following in relation to this experiment:
$(a)$ Name the element he selected for this purpose.
$(b)$ Which subatomic particle was used by him?
$(c)$ What was the drawback of Rutherford's model of the atom?