Question

Which of the following element belongs to the third transition series of the periodic table?

(a) Sc

(b) Re

(c) Rh

(d) Tc

This question was addressed to me in semester exam.

My enquiry is from Position of the Periodic Table in section D and F-Block Elements of Chemistry – Class 12

Answer 1

Right option is (b) Re

Best explanation: The third transition series or 5d series corresponding to the filling of 5d sublevel consists of the following 10 elements of the 6^th period: La (Atomic No. = 57); Hf (Atomic No. = 72), Ta, W, Re, Os, Ir, Pt, Au and Hg (Atomic No. = 80).