On moving from left to right in a period of the periodic table, the atomic number of elements increases. What happens to the size of atoms of elements on moving from left to right in a period?

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?