Question

Total number of d-electron present in an element having atomic number 78 is (1)8
(2)28
(3)29
(4)19

Answer 1

first of all we write configuration of this elements .
e.g ,
1s², 2s², 2p^6, 3s² , 3p^6, 4s² , 3d^10, 5s²,4d^10 ,5p^6, 6s^2, 4f¹⁴, 5d^10 , 6p⁴

but due to extra ability of complete filled , configuration goes to
[ Xe] 4f¹⁴, 5d^9, 6s¹

hence, no of total d -electrons = 10 + 10 + 9 = 29

Answer 2

Answer:

Explanation:abhi where is 4p6 shell????