$J. Chadwick$ discovered a subatomic particle which has no charge and has a mass nearly equal to that of a proton. Name the particle and give its location in the atom.

Sulphur dioxide $(SO_{2})$ is a colourless,pungent-smelling gas and is a major air pollutant.
$(a)$ Write the electronic configuration of its constituent elements,sulphur and oxygen.
(Given: $_{16}^{32}S, _{8}^{16}O)$
$(b)$ Write the valency of sulphur and oxygen.
$(c)$ Are sulphur and oxygen isotopes of the same element? Explain your answer.

The electronic configuration of an element $X$ is $2, 8, 2$.
$(a)$ Find the number of electrons present in the atom of element $X$.
$(b)$ Write the atomic number.
$(c)$ Is this element $X$ a metal or a non-metal?
$(d)$ Find out the valency of the element $X$.

An ion $Y^{3-}$ contains $18$ electrons and $16$ neutrons. Calculate the atomic number and mass number of the element $Y$. Name the element $Y$.

Which of the following statements about Rutherford's model of the atom are correct?
$(i)$ Considered the nucleus as positively charged.
$(ii)$ Established that the $\alpha$-particles are four times as heavy as a hydrogen atom.
$(iii)$ Can be compared to the solar system.
$(iv)$ Was in agreement with Thomson's model.

State whether the following statement is true or false:
In water,the ratio of the mass of hydrogen to the mass of oxygen is always $1:8$,regardless of the source of water.