Electron Configuration Transition Metals

[Hemichordate]

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What compounds, besides Copper and Chromium, have ground electron configurations that have 4s1 instead of 4s2 (followed by a partially or completely filled d shell)?

i.e.

Copper has [Ar] 3d10 4s1

Chromium has

[Ar] 3d5 4s1

 

[ilovemcat]

What compounds, besides Copper and Chromium, have ground electron configurations that have 4s1 instead of 4s2 (followed by a partially or completely filled d shell)?

i.e.

Copper has [Ar] 3d10 4s1

Chromium has

[Ar] 3d5 4s1

An easy way to remember this is by glancing at the Periodic Table, and looking for elements that want Half-filled d-hell or Filled d-shell stability. The transition metals span the rows 1-10 (Transition Metal Section). The elements in Row 4 exhibit half-filled d-shell stability (they want 5 electrons in their d-shell because it's more stable to have 1 electron in each subshell). The elements in Row 9 exhibit filled d-shell stability. (they prefer to have 10 electrons in their d-shell).

Half-filled d shell stability:
- Cr
- Mo

Filled d shell stability:
- Cu
- Ag
- Au

 

[Hemichordate]

Great! Thanks. Do group 4 and 9 metals also form stronger bonds due to the excited electron?

 

[Don Draper]

An easy way to remember this is by glancing at the Periodic Table, and looking for elements that want Half-filled d-hell or Filled d-shell stability. The transition metals span the rows 1-10 (Transition Metal Section). The elements in Row 4 exhibit half-filled d-shell stability (they want 5 electrons in their d-shell because it's more stable to have 1 electron in each subshell). The elements in Row 9 exhibit filled d-shell stability. (they prefer to have 10 electrons in their d-shell).

Half-filled d shell stability:
- Cr
- Mo

Filled d shell stability:
- Cu
- Ag
- Au

another thing BR drills on that I highly doubt the MCAT would test. I would know the idea of half filled stability, but them testing this is not likely.

 

[ilovemcat]

another thing BR drills on that I highly doubt the MCAT would test. I would know the idea of half filled stability, but them testing this is not likely.

If they did that, they'd be punks for doing that.
But yeah there's also half-filled and filled stability for the p orbital and s orbital respectively, which deviate from your normal trends for Ionization Energy and Electron Affinity.

Be and Nitrogen are two such examples. To answer these questions, look at what the question is asking and relate it to the stabilities of the elements:

Energy of Ionization - The energy needed to pull an electron. (Both of the following are more stable so you expect electrons to be harder to pull off).
- Be has a higher Energy of Ionization than Boron, but lower than Carbon.
- Nitrogen has a higher Energy of Ionization than Oxygen, but lower than F.

Electron Affinity - The energy released upon adding an electron.
Although the trend increases in Affinity as you go DOWN the column and UP each ROW (energy released, more negative), Be, Mg, as well as N and P all exhibit much more positive Electron Affinities (energy must be added) because they're in a much more stable form.

These are exceptions which are unlikely to be tested on the exam, but it's worth noting just incase.

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And be careful, the electron for those half-filled transition metals aren't "excited". Instead 1 electron from the 4s orbital is promoted to a higher energy level to produce a more stable form. Without going too much in detail, the reason for this is because the 4s shell and 3d shell occupy about the same distance from the atom and have very close energies. But if you're every asked to compare which shell has a higher energy, it's the order their filled - so the 3d shell would have the higher energy.