Question

Which of the following atomic numbers is not matched with their correct electronic configuration?

• A. $24:1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^5$
• B. $46:1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^8$
• C. $47:1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{4}4p^{6}5s^{1}4d^{10}$
• D. $29:1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{10}$

Answer 1

The correct option is B $46:1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^8$

The element with atomic number 46 is palladium. As per Aufbau principle one can expect the electronic configuration: $46:1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^8$
Since completely filled d orbitals are more stable than partially filled d orbitals, the configuration of palladium is $46:1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{0}4d^{10}$