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Classification of Elements and Periodicity in Properties
Question
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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

Answer

C.

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

Electronic configuration of 63Eu [europium ]
= [Xe] 4f7  6s2, 
Electronic configuration of 64Gd [gadolinium ]
= [Xe] 4f7 5d1 6s2 
Electronic configuration 65Tb [terbium]
= [Xe] 4f9 6s2 

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Some More Questions From Classification of Elements and Periodicity in Properties Chapter

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.