Explain the position of lanthanoids in the periodic table. OR How is

1.	Explain the position of lanthanoids in the periodic table. OR How is the position of lanthanoids justified?
Answer» 1. Position of Lanthanoids in the periodic table : Group – 3; Period – 6. 2. They interrupt the third transition series of t/-block elements (i.e. 5 d series) in the sixth period. 3. They are 14 elements from ₅₈Ce to ₇₁Lu and their position is in between La and Hf. Since they follow lanthanum, they are called lanthanoids. 4. They are called 4f-series elements and for the convenience, they are placed separately below the main periodic table. 5. The actual position of lanthanoids is in between Lanthanum (Z = 57) and Hafnium (Z = 72). 6. Their position is justified due to following reasons : All these elements have the same electronic configuration in ultimate and penultimate shells, one electron in 5d-orbital and two electrons in 6s-orbital. Group valence of all lanthanoids is 3. All lanthanoids from ₅₈Ce to ₇₁Lu have similar physical and chemical properties.

Explain the position of lanthanoids in the periodic table. OR How is the position of lanthanoids justified?

Answer»

1. Position of Lanthanoids in the periodic table : Group – 3; Period – 6.

2. They interrupt the third transition series of t/-block elements (i.e. 5 d series) in the sixth period.

3. They are 14 elements from ₅₈Ce to ₇₁Lu and their position is in between La and Hf. Since they follow lanthanum, they are called lanthanoids.

4. They are called 4f-series elements and for the convenience, they are placed separately below the main periodic table.

5. The actual position of lanthanoids is in between Lanthanum (Z = 57) and Hafnium (Z = 72).

6. Their position is justified due to following reasons :

All these elements have the same electronic configuration in ultimate and penultimate shells, one electron in 5d-orbital and two electrons in 6s-orbital.
Group valence of all lanthanoids is 3.
All lanthanoids from ₅₈Ce to ₇₁Lu have similar physical and chemical properties.