Solved Identify whether the following orbital diagrams | Chegg.com - Free Printable

Let's analyze each orbital diagram and identify which quantum mechanical principle it violates, using the Answer Bank:
- Aufbau Principle (electrons fill orbitals from lowest to highest energy)
- Hund’s Rule (electrons fill degenerate orbitals singly before pairing up)
- Pauli Exclusion Principle (no two electrons in the same orbital can have the same spin; max 2 electrons per orbital with opposite spins)

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Top Left Diagram:

- 5s: ↑ (1 electron — okay)
- 3d: ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ (all 5 orbitals filled with paired electrons — okay for 10 electrons)
- 4s: ↑↓ (filled — okay)

✔ No violation. All principles followed.

> *But wait — the 5s orbital is filled before 4s? That’s a problem!*

Actually, the order of filling is 4s before 3d, and 5s should be filled after 4p, not before 4s. Here, 5s has an electron while 4s is already full — that’s fine if we’re talking about an excited state, but if this is meant to represent ground state electron configuration, then electrons are placed in higher energy orbitals (5s) before lower ones (like 4p or even 3d is already filled) — but 3d is filled, 4s is filled, so 5s shouldn’t be occupied until after 4p.

However, looking more carefully — the 5s orbital is shown with one electron, and 4s is filled. In ground state, 4s fills before 3d, and 5s fills after 4p. But here, 3d is filled (which comes after 4s), so maybe this is after 4s and 3d are filled — then 5s could be next. BUT — the 5s orbital is shown above 3d and 4s, implying incorrect energy ordering.

Actually, the bigger issue is: if 4s is filled and 3d is filled, then 5s should not be occupied until after 4p — but 4p isn’t even shown. So perhaps the diagram implies electrons are being placed in 5s before 4p, violating the Aufbau Principle.

Wait — let’s look again. The diagram shows:

- 5s: ↑
- 3d: all filled (↑↓ x5)
- 4s: ↑↓

This suggests 5s is occupied before 4p, which hasn’t been filled yet. Since 4p orbitals are lower in energy than 5s, this violates the Aufbau Principle.

✔ Violation: Aufbau Principle

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Top Right Diagram:

- 2p: ↑↓ ↑ ↑ (first orbital has 2 electrons with same spin? Wait — no, ↑↓ means one up, one down — that’s fine. But there are 3 orbitals: first has ↑↓, second ↑, third ↑ → total 4 electrons in 2p? That’s possible, but check spins.)

Actually, in the first 2p orbital: both arrows point UP? Looking closely — in the image, the first box in 2p has two up arrows — that’s two electrons with the same spin in the same orbital.

That directly violates the Pauli Exclusion Principle, which states that no two electrons in the same orbital can have identical quantum numbers — including spin. They must have opposite spins (↑↓).

✔ Violation: Pauli Exclusion Principle

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Middle Left Diagram:

- 4d: ↑↓ ↓ ↑ ↑ ↑ (first orbital: ↑↓ — okay; second: ↓ — okay; third: ↑ — okay; fourth: ↑ — okay; fifth: ↑ — okay)
- 5s: ↑↓ — okay

But look at the 4d orbitals: they are degenerate (same energy). According to Hund’s Rule, electrons should occupy orbitals singly with parallel spins before pairing.

Here, the first 4d orbital is already paired (↑↓), while the other four orbitals have only one electron each — but they are NOT all aligned with the same spin.

Specifically:
- Orbital 1: ↑↓ (paired)
- Orbital 2: ↓ (down spin)
- Orbital 3: ↑ (up spin)
- Orbital 4: ↑
- Orbital 5: ↑

So, we have one orbital paired while others are singly occupied with mixed spins. This violates Hund’s Rule, which requires:
1. Maximize unpaired electrons (so don’t pair until necessary)
2. All unpaired electrons should have same spin

Here, pairing occurred too early (orbital 1 is paired while others are empty or singly occupied), and spins are not maximized/parallel.

✔ Violation: Hund’s Rule

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Middle Right Diagram:

- 3p: ↑ ↑ ↑ (three orbitals, each with one electron, all spin up — good!)
- 3s: ↑ (only one electron — should be ↑↓ if full, but it’s not full — okay for now)

Wait — 3s has only one electron? That’s fine if it’s not full. But the 3s orbital should be filled before 3p according to Aufbau Principle.

Here, 3s has only one electron (↑), and 3p has three electrons (↑ ↑ ↑). That implies 3p is being filled before 3s is complete.

The 3s orbital can hold 2 electrons. It only has 1. So electrons are going into 3p before 3s is filled — this violates the Aufbau Principle.

✔ Violation: Aufbau Principle

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Bottom Left Diagram:

- 3d: ↑↓ _ _ _ _ (only first orbital filled, rest empty)
- 4s: ↑↓ (filled)

This is clearly wrong. For 3d orbitals (5 orbitals), electrons should fill them singly first (Hund’s Rule) before pairing.

Here, only one 3d orbital is filled (with a pair), while the other four are completely empty. That violates Hund’s Rule, because you should put one electron in each 3d orbital before pairing any.

Also, if this is meant to represent a ground state, 4s is filled before 3d, which is correct — but once you start filling 3d, you must follow Hund’s Rule.

✔ Violation: Hund’s Rule

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## ✔ Final Answers:

| Orbital Diagram | Violation |
|------------------|--------------------------|
| Top Left | Aufbau Principle |
| Top Right | Pauli Exclusion Principle |
| Middle Left | Hund’s Rule |
| Middle Right | Aufbau Principle |
| Bottom Left | Hund’s Rule |

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📌 Summary:

- Aufbau Principle violated when electrons occupy higher energy orbitals before lower ones are filled.
- Pauli Exclusion Principle violated when two electrons in same orbital have same spin.
- Hund’s Rule violated when electrons pair prematurely or don’t maximize parallel spins in degenerate orbitals.

These are the core rules governing electron configurations in atoms.