Question

The set that contains atomic numbers of only transition elements is:

• A. $37,42,50,64$
• B. $21,32,53,64$
• C. $21,25,42,72$
• D. $9,17,34,38$

Answer 1

The correct option is C $21,25,42,72$

A transition element is defined as the one which has incompletely filled d-orbitals in its ground state or in general oxidation state.
The first transition element series have Z= 21 to 29
The second transition element series have Z= 39 to 47
The third transition element series have Z= 57,72 to 79
Elements of option (c) only falls in the region and is the correct option.