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State the genral electronic configuration of elements of actinoid series. Why there are irregularities in the electronic configurations? |
Answer» Solution :The general electronic configuration of elements of actinoid series is `[Rn] 5f^(0-14) 6d^(0-2) 7s^(2)`. In tripositive state, the configuration is `5f^(N)` (n=1 to 14). Except actinium and thorium in tetrapositive state, the configuration is `5f^(n)` (n=1 to 13)  Reason for irregularities: The irregularities in the electronic configuration of actinoid series is due to very less difference in the energies of 5f and 6d orbitals. All actinoids believe to have the electronic configuration of `7s^(2)` and variable occupancy of 5f and 6d subshells. From protactinium (PA) the 14 electrons are added successively in 5f-orbitals till lawrencium. The irregularities in the configuration of actinoids are related to the STABILITIES of `f^(0), f^(7) and f^(14)` occupancies of 5f-orbitals. Thus the configurations of Am and CM are `[Rn]4f^(7) 7s^(2) and [Rn] 5f^(7) 6d^(1) 7s^(2)` respectively. Due to presence of one d-electron in actinium and lawrencium, these elements are some time considered as group 3 elements |
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