Question

Two students were analysing the electronic configurations of the first 30 elements of the Periodic Table as part of an assignment. They found that two elements showed difference from other twenty eight elements. 

1. Which are the two elements? 

2. Write their electronic configurations. 

3. Why they show this anomalous behaviour?

Answer 1

1. ₂₄Cr and ₂₉Cu. 

2. ₂₄Cr = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵ and 

₂₉Cu = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰ 

3. This is due to the fact that exactly half filled and completely filled orbitals (i.e.,d⁵, d¹⁰) have extra stability due to symmetrical distribution of electrons and maximum exchange energy.