Which of the following pairs of elements belong to the same period?

Which and how many blocks are present in the periodic table? Explain the factors upon which this classification depends.

Atomic numbers of three elements $E_1$,$E_2$ and $E_3$ of the periodic table are $Z_1$,$50$ and $Z_2$ respectively. From the position of the elements shown in the figure,the value of $(Z_2 - Z_1)$ is:

Element $E$ belongs to the period $4$ and group $16$ of the periodic table. The valence shell electron configuration of the element,which is just above $E$ in the group is $.....$

What will be the $IUPAC$ symbol and name for the element with atomic number $123$?

Choose the correct $IUPAC$ symbol and $IUPAC$ official name for the element with atomic number $108$.