Question

4d series present in 5 th period elements each 10 element

Answer 1

The 4d series in the 5th period contains 10 elements because the d-orbital can accommodate 10 electrons.

Answer 2

The d-subshell has 5 orbitals and can hold a maximum of 10 electrons (each orbital holding 2 electrons). Thus, when adding electrons to the d-subshell, 10 electrons (or 10 successive elements) complete that subshell. In the periodic table, the 4d series (which appears in the 5th period) spans 10 elements: from yttrium (Y, Z=39) to cadmium (Cd, Z=48).