Which of the following are the correct characteristics of isotopes of an element?
i. Same atomic mass
ii. Same atomic number
iii. Same physical properties
iv. Same chemical properties

The atomic numbers of three elements $\mathrm{X}, \mathrm{Y}$ and $\mathrm{Z}$ are $2, 6$ and $10$ respectively.

Which two elements belong to same group?

The atomic numbers of three elements $\mathrm{X}, \mathrm{Y}$ and $\mathrm{Z}$ are $2, 6$ and $10$ respectively.

Which two elements belong to same period?

An atom has the electron structure $2, 7$.

What is the atomic number of this atom?

An atom has the electron structure $2, 7$. To which of the following the atom would be similar and why?

${}_7{}^{}\mathrm{N}, {}_{15}{}^{}\mathrm{P}, {}_{17}{}^{}\mathrm{Cl}, {}_{18}{}^{}\mathrm{Ar}$

Consider the following elements: ${}_{20}{}^{}\mathrm{Ca}, {}_8{}^{}\mathrm{O}, {}_{18}{}^{}\mathrm{Ar}, {}_{16}{}^{}\mathrm{S}, {}_4{}^{}\mathrm{Be}, {}_2{}^{}\mathrm{He}$

Which of the above elements would you expect to be very stable?

Consider the following elements: ${}_{20}{}^{}\mathrm{Ca}, {}_8{}^{}\mathrm{O}, {}_{18}{}^{}\mathrm{Ar}, {}_{16}{}^{}\mathrm{S}, {}_4{}^{}\mathrm{Be}, {}_2{}^{}\mathrm{He}$

Which of the above elements would you expect to be in group $2$ of the periodic table?

Consider the following elements: ${}_{20}{}^{}\mathrm{Ca}, {}_8{}^{}\mathrm{O}, {}_{18}{}^{}\mathrm{Ar}, {}_{16}{}^{}\mathrm{S}, {}_4{}^{}\mathrm{Be}, {}_2{}^{}\mathrm{He}$

Which of the above elements would you expect to be in group $16$ in the periodic table?