The electronic configuration of Eu (Atomic no.63), Gd (Atomic no. 64) and Tb (Atomic no. 65) are

• [Xe]4f⁶ 5d¹ 6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹  6s² 

• [Xe] 4f⁶ 5d¹ 6s² , [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁸ 5d¹ 6s² 

• [Xe] 4f⁷  6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹ 6s² 

• [Xe] 4f⁷  6s²,[Xe] 4f⁸  6s² and [Xe] 4f⁸ 5d¹ 6s²

What is the number of groups in: (i) p-block  (ii) d-block?

How many elements are present in:
(i) second period    
(ii) fourth period    
(iii) sixth period?

What is the name given to the s-block elements?

To which block the element with outer electronic configuration 4s²3d¹⁰ belongs?

Why are there 10 elements in each series of d-block?

In terms of electronic configuration,
what is common in a given period and group?

Give the general electronic configuration of
(i) Transition elements     (ii) Inner transition elements.

Name the group and period to which an element with Z = 15 belongs ?

What are the advantages of periodic classification of elements?

In the modern periodic table, the period indicates the value of:
(a) atomic number
(b) atomic mass
(c) principal quantum number
(d) azimuthal quantum number.