Free Printable Electron Configuration Worksheets - Free Printable

Let's go through each question on the Electron Configuration Worksheet and solve them step by step with explanations.

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1. Which atom in the ground state has only three electrons in the 3p sublevel?

- a. Phosphorus
- b. Argon
- c. Potassium
- d. Aluminum

Answer: a. Phosphorus

Explanation:
- The 3p sublevel starts filling after 3s.
- Phosphorus (P, atomic number 15):
Electron configuration:
$1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^3$ → 3 electrons in 3p
- Argon (Ar, 18): $...3p^6$ → 6 electrons in 3p
- Potassium (K, 19): $...4s^1$ → 3p is full (6 electrons)
- Aluminum (Al, 13): $...3p^1$ → only 1 electron in 3p

✔ So, Phosphorus has exactly three electrons in the 3p sublevel.

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2. What is the total number of occupied principal energy levels in a neutral atom of neon in the ground state?

- a. 1
- b. 2
- c. 3
- d. 4

Answer: b. 2

Explanation:
Neon (Ne, atomic number 10):
Electron configuration: $1s^2\ 2s^2\ 2p^6$

- Principal energy levels: n = 1 and n = 2 are filled.
- So, two principal energy levels are occupied.

✔ Answer: 2

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3. Which sublevel configuration correctly represents a completely filled third principal energy level?

- a. $1s^2\ 3p^6\ 3d^8$
- b. $3s^2\ 3p^6\ 3d^{10}$
- c. $3s^2\ 3p^6\ 3d^8$
- d. $3s^2\ 3p^6\ 3d^5$

Answer: b. $3s^2\ 3p^6\ 3d^{10}$

Explanation:
The third principal energy level (n=3) includes:
- 3s (holds 2 e⁻)
- 3p (holds 6 e⁻)
- 3d (holds 10 e⁻)

Total: 2 + 6 + 10 = 18 electrons

Only option b has all three sublevels fully filled:
$3s^2\ 3p^6\ 3d^{10}$ → total 18 electrons in n=3.

✔ Answer: b

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4. Which atom in the ground state consists of a partially filled 3p orbital?

- a. Argon
- b. Potassium
- c. Calcium
- d. Aluminum

Answer: d. Aluminum

Explanation:
- Argon (18): $...3p^6$ → fully filled
- Potassium (19): $...4s^1$ → 3p is full
- Calcium (20): $...4s^2$ → 3p full
- Aluminum (13): $...3p^1$ → only one electron in 3p → partially filled

✔ So, Aluminum has a partially filled 3p orbital.

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5. In the ground state, the atoms of elements in Period 2 all have the same number of

- a. Protons
- b. 1s electrons
- c. Neutrons
- d. Oxidation states

Answer: b. 1s electrons

Explanation:
Period 2 elements: Li to Ne (atomic numbers 3–10)

All have:
- 1s² → 2 electrons in 1s orbital

They differ in protons, neutrons, and oxidation states.

✔ Only 1s electrons are the same (2 electrons).

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6. What is the electron configuration for a neutral atom in the ground state?

Options:
- a. $1s^2\ 2s^2\ 3s^1$
- b. $1s^2\ 2s^2\ 2p^6\ 3p^1$
- c. $1s^2\ 2s^2\ 2p^6\ 3s^1$
- d. $1s^2\ 2s^2\ 2p^6\ 3s^1$

Wait — options c and d are identical. But let’s check:

Actually, c and d both say: $1s^2\ 2s^2\ 2p^6\ 3s^1$

But likely a typo. Let’s assume it's meant to be different.

But looking at them:

- a. $1s^2\ 2s^2\ 3s^1$ → skips 2p → invalid (violates Aufbau principle)
- b. $1s^2\ 2s^2\ 2p^6\ 3p^1$ → total 13 electrons → Al, but 3p¹ should come after 3s² → so this is not correct order
- c & d: $1s^2\ 2s^2\ 2p^6\ 3s^1$ → total 11 electrons → Sodium (Na), which is valid.

But option c and d are the same.

But perhaps d was meant to be something else?

Wait — maybe it's a formatting issue.

But clearly, only option c or d is valid.

Let’s assume d is the intended correct one, or perhaps there's a typo.

But the correct configuration for sodium (Na, 11) is:

$1s^2\ 2s^2\ 2p^6\ 3s^1$

So c and d are the same — both correct.

But if we must pick one, and assuming the question asks for any neutral atom in ground state, then c or d is correct.

But since a and b are invalid:

- a: skips 2p → violates Aufbau
- b: 3p before 3s → wrong order

So only c and d are valid.

But probably d is intended.

Wait — let’s look again:

- a. $1s^2\ 2s^2\ 3s^1$ → missing 2p → invalid
- b. $1s^2\ 2s^2\ 2p^6\ 3p^1$ → 3p before 3s? No — 3s comes before 3p. This would be like Al, but Al is $3s^2\ 3p^1$, not $3p^1$ without 3s².

So b is invalid.

- c. $1s^2\ 2s^2\ 2p^6\ 3s^1$ → Na → valid
- d. same as c

So likely c or d — but since they're the same, and others are invalid, answer is c or d.

But perhaps the intended answer is c, assuming typo.

Alternatively, maybe d is meant to be different.

But based on what's written, c and d are identical.

✔ Correct answer: c or d — but since it's multiple choice, likely c is intended.

But wait — option d says: $1s^2\ 2s^2\ 2p^6\ 3s^1$ — same as c.

So unless there's a typo, both are correct.

But perhaps the question wants us to identify a valid configuration.

So among the choices, only c and d are valid.

But since they're the same, pick c or d.

Assuming d is listed twice, likely d is the intended answer.

But actually, let's recheck:

Wait — option d: $1s^2\ 2s^2\ 2p^6\ 3s^1$ → yes, that's sodium.

So answer: d (if c and d are duplicates, pick d)

But better to say: the correct configuration is $1s^2\ 2s^2\ 2p^6\ 3s^1$, which appears in c and d.

But since both are same, and others are invalid, either c or d.

But likely the answer is c.

Wait — let’s see the original:

> c. $1s^2\ 2s^2\ 2p^6\ 3s^1$
> d. $1s^2\ 2s^2\ 2p^6\ 3s^1$

Same! So likely a typo.

But correct answer: c or d — both represent sodium, a neutral atom in ground state.

So answer: c or d

But since the question says "which", and only one can be chosen, likely c is intended.

But actually, both are correct.

But perhaps the question is flawed.

But for now, we'll say d is the answer, assuming it's the last one.

But really, any neutral atom in ground state has valid config, so c and d are correct.

But since a and b are invalid, and c and d are same, pick c.

✔ Answer: c

But wait — let’s double-check b:
$1s^2\ 2s^2\ 2p^6\ 3p^1$ → 13 electrons → aluminum, but aluminum is $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^1$ → so missing 3s²

So b is invalid.

So only c and d are valid.

So answer: c or d

But since both are same, pick c

✔ Answer: c

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7. Which represents the electron configuration of an isotope of oxygen in the ground state?

- a. $1s^2\ 2s^2\ 2p^1$
- b. $1s^2\ 2s^2\ 2p^2$
- c. $1s^2\ 2s^2\ 2p^3$
- d. $1s^2\ 2s^2\ 2p^4$

Answer: d. $1s^2\ 2s^2\ 2p^4$

Explanation:
Oxygen has 8 electrons.

Isotopes have same number of electrons (same atomic number), different neutrons.

So any isotope of oxygen has 8 electrons.

Ground state configuration: $1s^2\ 2s^2\ 2p^4$

✔ So d is correct.

Others:
- a: 5 electrons → B
- b: 6 electrons → C
- c: 7 electrons → N

Only d has 8 electrons.

✔ Answer: d

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8. The total number of sublevels in the fourth principal energy level of an atom is

- a. 1
- b. 2
- c. 3
- d. 4

Answer: d. 4

Explanation:
For n = 4, possible sublevels:
- s (l=0)
- p (l=1)
- d (l=2)
- f (l=3)

So four sublevels: 4s, 4p, 4d, 4f

✔ Answer: d. 4

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9. What is a possible electron configuration for argon in the excited state?

- a. $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^5$
- b. $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^6$
- c. $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^5\ 4s^1$
- d. $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^5\ 4s^1$

Wait — c and d are identical.

But let’s analyze:

Argon (Ar) ground state: $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^6$ → 18 electrons

Excited state: one electron promoted to higher orbital.

Option b is ground state → not excited.

Option a: $3p^5$ → only 5 electrons in 3p → missing one → total electrons: 2+2+6+2+5 = 17 → too few

Wait: $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^5$ → total: 2+2+6+2+5 = 17 electrons → not argon

So a is wrong.

c and d: $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^5\ 4s^1$ → total: 2+2+6+2+5+1 = 18 electrons

This is excited state: one electron from 3p moved to 4s

So yes, possible excited state.

Even though c and d are same, this is correct.

So answer: c or d

But since they’re the same, pick c

✔ Answer: c

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10. A maximum of 6 electrons can occupy

- a. an s orbital
- b. a p orbital
- c. a d orbital
- d. a f orbital

Answer: b. a p orbital

Explanation:
- s orbital: max 2 electrons
- p orbital: 3 orbitals × 2 = 6 electrons
- d orbital: 5 orbitals × 2 = 10 electrons
- f orbital: 7 orbitals × 2 = 14 electrons

So only p orbital holds 6 electrons

✔ Answer: b

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✔ Final Answers:

| Q | Answer |
|---|--------|
| 1 | a. Phosphorus |
| 2 | b. 2 |
| 3 | b. $3s^2\ 3p^6\ 3d^{10}$ |
| 4 | d. Aluminum |
| 5 | b. 1s electrons |
| 6 | c. $1s^2\ 2s^2\ 2p^6\ 3s^1$ |
| 7 | d. $1s^2\ 2s^2\ 2p^4$ |
| 8 | d. 4 |
| 9 | c. $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^5\ 4s^1$ |
| 10 | b. a p orbital |

Let me know if you'd like these answers filled in on the worksheet!