In Universe , recently discovered by an intrepid team of chemists who also happen to have studied interdimensional travel, quantum mechanics works just as it does in our universe, except that there are eight orbitals instead of the usual number we observe here. Use these facts to write the ground-state electron configurations of the seventh and eighth elements in the first transition series in Universe . Note: you may use to stand for the electron configuration of the noble gas at the end of the row before the first transition series.

Sixth transition element: [X] 3d8 4s0

Seventh transition element: [X] 3d8 4s0

Explanation:

In the universe, we have 5 number of "d" orbitals.

Now, Aufbau's rule states that in the ground state of an atom/ion, the electrons will usually fill atomic orbitals of the lowest available energy levels before they occupy higher levels. Meanwhile Hund's rule states that all orbitals in a subshell will be singly occupied with one electron before any single orbital is doubly occupied, and also all electrons in singly occupied orbitals will have the same spin.

From the periodic table, we know that the 6th & 7th transition elements in the universe are Iron & cobalt respectively. Their respective electronic configuration are;

Iron - [Ar] 3d6 4s2

Cobalt - [Ar] 3d7 4s2

Now, in the new universe(L) where there are 8 d - orbitals: from a combination of aufbau's rule and hund's rule; since there are six numbers of d orbitals as earlier said, in iron, which is the sixth transition metal, due to the fact that half filled orbitals will be more stable than partially filled orbitals, it means the 4s orbital will be empty and then two electrons will be removed from the 4s and used to fill the 3d orbital to half way.

Thus, ground state configurations of

Iron = [X] 3d8 4s0

Similarly, for the 7th transition element which is cobalt, the new extra electron will just fill the lower energy orbital which is 4s,thereby leaving the eight numbers of 3d orbitals to be half filled.

Thus, ground state configurations of

Cobalt = [X] 3d8 4s1

Therefore their ground state configurations are;

- Sixth transition element: [X] 3d8 4s0

Seventh transition element: [X] 3d8 4s1

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