Question

The Lanthanides and Actinides are placed in group number

Answer 1

Hint : We know that lanthanide series consists of fourteen elements following the lanthanum element. F-block elements consist of two series Lanthanoid and Actinoid, they are placed in group three. They occupy period six and period seven of the periodic table respectively.

Complete Step By Step Answer:
The modern periodic table consists of $118$ elements arranged in a total of eighteen groups and seven periods. The vertical columns represent the groups and the horizontal rows represent the periods. We know there are four different blocks in the periodic table. Each block corresponds to the filling of electrons in the corresponding orbital as mentioned in their name. For example the f- block corresponds to the following of electrons in the f- orbital of the atoms. These elements make up the f- block. The f-block consists of two periods. The first period elements that correspond to the filling of $4f-$ orbital are known as Lanthanide while the second period elements in the f- block that correspond to the filling of $5f-$ orbitals are actinides. Collectively, both lanthanides and actinides are known as the f block elements.
Lanthanides and actinides are in periods six and seven, respectively. Generally, they are placed underneath the periodic table. The lanthanides are between Barium and Hafnium. The actinides are between Radium and Rutherfordium. Lanthanides and actinides are in periods six and seven, respectively.

Note :
Remember that the Lanthanide series consists of $14$ elements which follow lanthanum. The f block elements are placed at the bottom of the periodic table. Also the f block elements are called inner transition series. Lanthanum closely resembles Lanthanoid.