Write the postulates of Dalton’s atomic theory.

Iron filings are mixed with sulphur powder, what do you observe when

(i) a magnet is brought near the mixture.

(ii) the mixture is mixed with carbon disulphide.

What will you observe when zinc granules are added to dilute sulphuric acid?

Which two of the following species are isotopes of each other and which two are isobars.

${}_{90}{}^{231}\mathrm{X}$, ${}_{91}{}^{230}\mathrm{Y}$, ${}_{88}{}^{230}\mathrm{Z}$, ${}_{90}{}^{233}\mathrm{X}$.