Respuesta :
Explanation:
The atomic number of Uranium is 92. The electron configuration is: [U] = [Rn] 5f3; 7s4 where Radon Rn has 86 electrons and a complete period. This result is respecting the Madelung. BUT … U is an exception !!!
On the period 7 are only 6 electron left for Uranium (92–86). The first 2 electrons are on the principal energy level 7 and occupy the 7s-orbital block. The 3rd electron is placed in the 5f-orbital block. The next 3 electrons are place here as well. The last electron has the unique quantum label (n; l; ml; s) = (5; 3; 0; 0)
To understand this: The first electron of the 5f-orbital block has the label (5; 3, -3; 0). The following electrons have the labels (5; 3; -2, 0), (5; 3; -1; 0), (5; 2; 0; 0). You notice, that the HUND’S RULE is satisfied. ( I always use head 0 before tail 1 to represent the spin.) The f-orbital block is made up of 7 orbitals and therefore can be filled up by at most 14 electrons. When the first electron has the spin 0 then the next 6 electrons must also have the spin 0. With the electron 8 you get the label (5; 3; -3, 1) which tells us, that the spin is opposite to 0. It must be 1. The next 6 electrons also will have spin 1 but are placed in the orbitals -2; -1; 0; 1; 2; 3. Their labels are: (5; 3; -2; 1), (5; 3; -1; 1), (5; 3; 0; 1), (5; 3; 1; 1), (5; 3; 2; 1) and (5; 3; 3; 1) Now the f-block is full !!!
ANSWER: The last electron of U has the label (5; 3; 0; 0). BUT … !!!!!
I hope that you can verify now the correctness of the answer by yourself according to the Madelung.
Please, apply the definitions of the 4 quantum numbers correctly by also respecting the MANDELUNG’S RULE, the OCTET RULLE, the HUND’S RULE.
NOTICE: The Madelung has 21 exceptions. (Wikipedia lists only 20 and treats Ni not as an exception)
Cr, Ni, Cu, Nb, Mo, Ru, Rh, (Pd), Ag, Pt, Au and
La, Ce, Gd, Ac, (Th), Pa, U, Np, Cm, Lr.
In the first group listed: 1 electron moves inwards. In the second group listed: 1 electron moves outwards. Pd and Th have 2 moving electron each. YOU CAN SEE, THAT U IS AN EXCEPTION !!!
CORRECT ANSWER: The last electron of U has the label (6; 2; 0; 0). Can you see the moving electron ??? ❮❮(5; 3; 0; 0) becomes (6; 2; 0; 0)❯❯ Can you see the moving outwards ???
The 21 exception were discovered with spectral analysis. The MADELUNG is not a principle !!! It is only a very simple rule to memorise the electron configurations. By respecting the exceptions, you can correct you Madelung answer !!! Learn the 21 exceptions by heart !
Did you get it ??? (6; 2; 0; 0) is the label of the last electron of U.
