Question

How many 'series' of transition elements are present in the periodic table?

• A. One
• B. Two
• C. Three
• D. Four

Answer 1

The correct option is D Four

Unlike s or p block elements which are usually discussed as groups, d-block elements are better discussed by classifying them into horizontal series. In the periodic table, there are four main transition series of elements corresponding to filling of 3d, 4d, 5d and 6d sublevels in the $4^{th},5^{th},6^{th}$ and $7^{th}$ periods.