CBSE Class 11-science Answered

The Transition metals are the elements found between the Group IIA elements and the Group IIB elements which include groups 3 to 12 on the periodic table. A transition series of elements is formed during the change of an inner layer of electrons (for example n=3 in the 4th row of the periodic table) from a stable group of 8 to one of 18, or from 18 to 32.

There are four transition series:

1. The first transition series: Scandium (Sc) through Copper (Cu): 3d sub shell is filling.
2. The second transition series: Yttrium (Y) through Silver (Ag): 4d sub shell is filling.
3. The third transition series: Lanthanum (La) to Hafnium (Hf) through Gold (Au)): 5d sub shell is filling.
4. The forth transition series is incomplete: Actinium (Ac) to element 104 through element 109: 6d sub shell is filling; if elements 110 and 111 are found then this will complete this series.