Question

Which of the following sets of atomic numbers corresponds to the atomic numbers of inert gases belonging to periods which contain 4d and 5d transition series?

• A. 54, 86
• B. 55, 87
• C. 36, 54
• D. 56, 85

Answer 1

The correct option is A 54, 86

Helium $1s^2$.................................................................................2

Neon $1s^{2}2s^{2}s2p^6$...............................................................10

Argon $1s^{2}2s^{2}s2p^{6}3s^{2}3p^6$..............................................18

Krypton $1s^{2}2s^{2}s2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^6$...............36

Xenon [Kr]$4d^{10}5s^{2}5p^6$.........................................................54

Radon [Xe] $4f^{14}5d^{10}6s^{2}6p^6$............................................86

So 54 and 86 have 4d and 5d orbits.