The average atomic mass of a sample of an element $y$ is $35.5 \,u$. What are the percentages of isotopes $_{17}^{37}y$ and $_{17}^{35}y$ in the sample?

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

Study the table given below and answer the questions that follow:

Particle	Electrons	Protons	Neutrons
$M$	$2$	$3$	$4$
$N$	$10$	$9$	$10$
$O$	$8$	$8$	$8$
$P$	$8$	$8$	$10$

$(a)$ Write the mass numbers of particles $M, N, O$ and $P$.
$(b)$ Select a cation and an anion from the above table.

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?

Write the atomic number of an element which has mass number $23$ and number of neutrons $12$ in the nucleus.

$(a)$ 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?