What is the electron configuration of arsenic?

Arsenic (As, Z=33) has the ground-state electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³. Its 33 electrons fill eight subshells across four principal shells.

What is the noble-gas shorthand for arsenic?

The condensed notation is [Ar] 3d¹⁰ 4s² 4p³, where [Ar] represents the filled 1s² 2s² 2p⁶ 3s² 3p⁶ core shared with argon.

How many valence electrons does arsenic have?

Arsenic has 5 valence electrons: 2 in the 4s subshell and 3 in the 4p subshell. This matches its Group 15 (VA) membership, directly below phosphorus.

Why does arsenic have three half-filled 4p orbitals?

Hund's rule states that electrons occupy separate orbitals of equal energy before pairing up. With 3 electrons in the 4p subshell, each of the three 4p orbitals holds exactly one unpaired electron, giving a half-filled subshell.

What oxidation states does arsenic form?

Arsenic most commonly shows −3 (in arsenides like Na₃As), +3 (in arsenious compounds like AsCl₃), and +5 (in arsenic acid H₃AsO₄). The +5 state uses the empty 4d orbitals for expanded bonding.

What block and period is arsenic in?

Arsenic is in Period 4, Group 15 (VA), and belongs to the p-block of the periodic table. It is classified as a metalloid.

How does arsenic's configuration compare to phosphorus?

Both are Group 15 elements with a half-filled outermost p subshell. Phosphorus is [Ne] 3s² 3p³; arsenic adds a filled 3p⁶ core and a full 3d¹⁰ shell relative to phosphorus, placing it in Period 4.

Is arsenic a metal or nonmetal?

Arsenic is a metalloid (also called a semimetal). It has some properties of metals (lustrous solid, brittle) and some of nonmetals (semiconducting, forms covalent compounds). Its 4p³ configuration gives it chemistry closer to nitrogen and phosphorus.

Arsenic Electron Configuration

Name: Arsenic Electron Configuration
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Author: Nham Vu

Reference tool for arsenic's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³), orbital box diagram, quantum numbers, and key atomic properties.

Z = 33 As Arsenic

Arsenic — Electron Configuration

Atomic number 33 · Metalloid · Period 4, Group 15 · p-block

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³ [Ar] 3d¹⁰ 4s² 4p³ 33 electrons 5 valence e⁻

Subshell Breakdown

Subshell	Type	Electrons	Max Capacity	Notation
1s	s orbital, shell n=1	2	2	1s²
2s	s orbital, shell n=2	2	2	2s²
2p	p orbitals, shell n=2	6	6	2p⁶
3s	s orbital, shell n=3	2	2	3s²
3p	p orbitals, shell n=3	6	6	3p⁶
3d	d orbitals, shell n=3	10	10	3d¹⁰
4s	s orbital, shell n=4	2	2	4s²
4p	p orbitals, shell n=4	3	6	4p³
Total		33

Full Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³

All subshells written explicitly.

Noble-Gas Shorthand

[Ar] 3d¹⁰ 4s² 4p³

[Ar] = 1s² 2s² 2p⁶ 3s² 3p⁶ (the filled argon core).

Shell Fill Summary

Shell 1 (n=1) — 1s² 2 / 2 electrons (100%)

Shell 2 (n=2) — 2s² 2p⁶ 8 / 8 electrons (100%)

Shell 3 (n=3) — 3s² 3p⁶ 3d¹⁰ 18 / 18 electrons (100%)

Shell 4 (n=4) — 4s² 4p³ 5 / 32 electrons (16%)

Shell 4 can hold up to 32 electrons (4s + 4p + 4d + 4f). Arsenic uses 5 of those 32 slots.

Orbital Box Diagram

2 electrons (paired) — filled

6 electrons across 3 orbitals — filled

2 electrons (paired) — filled

6 electrons across 3 orbitals — filled

10 electrons across 5 orbitals — filled

2 electrons (paired) — filled

3 electrons (one per orbital, all spin up) — Hund's rule

Each box represents one orbital. Opposing arrows show paired electrons with opposite spins (+½ and −½). Arsenic's three 4p electrons each occupy a separate orbital before any pairing occurs — this is Hund's rule, giving a half-filled 4p³ subshell.

Quantum Numbers for All 33 Electrons

Electron #	n	l	mₗ	mₛ	Subshell
1	1	0	0	+½	1s
2	1	0	0	−½	1s
3	2	0	0	+½	2s
4	2	0	0	−½	2s
5	2	1	-1	+½	2p
6	2	1	-1	−½	2p
7	2	1	0	+½	2p
8	2	1	0	−½	2p
9	2	1	1	+½	2p
10	2	1	1	−½	2p
11	3	0	0	+½	3s
12	3	0	0	−½	3s
13	3	1	-1	+½	3p
14	3	1	-1	−½	3p
15	3	1	0	+½	3p
16	3	1	0	−½	3p
17	3	1	1	+½	3p
18	3	1	1	−½	3p
19	3	2	-2	+½	3d
20	3	2	-2	−½	3d
21	3	2	-1	+½	3d
22	3	2	-1	−½	3d
23	3	2	0	+½	3d
24	3	2	0	−½	3d
25	3	2	1	+½	3d
26	3	2	1	−½	3d
27	3	2	2	+½	3d
28	3	2	2	−½	3d
29	4	0	0	+½	4s
30	4	0	0	−½	4s
31	4	1	-1	+½	4p
32	4	1	0	+½	4p
33	4	1	1	+½	4p

n = principal quantum number; l = azimuthal (l=0 → s, l=1 → p, l=2 → d); mₗ = magnetic; mₛ = spin. Electrons 31–33 each occupy a distinct 4p orbital with mₛ = +½ per Hund's rule.

Summary

Reference tool for arsenic's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³), orbital box diagram, quantum numbers, and key atomic properties.

How it works

The Aufbau principle fills orbitals from lowest to highest energy.
Arsenic's 33 electrons fill seven subshells: 1s, 2s, 2p, 3s, 3p, 3d, 4s, and 4p.
The 3d subshell holds 10 electrons across five orbitals, completing the d-block inner shell.
The 4p subshell holds 3 electrons — one per orbital with spin up, following Hund's rule.
Noble-gas notation replaces the inner filled shells with argon in brackets: [Ar] 3d¹⁰ 4s² 4p³.
The tabs below let you explore the full configuration, orbital diagram, and element data separately.

Use cases

Quick reference for chemistry homework or exam review on metalloid elements.
Visualize Hund's rule in action: three half-filled 4p orbitals in arsenic.
Understand why arsenic commonly shows −3, +3, and +5 oxidation states.
Compare arsenic to neighboring elements germanium and selenium in Period 4.
Teaching aid for d-block electron filling and transition from metals to metalloids.
Verify quantum numbers for each of arsenic's 33 electrons.
Explore how the half-filled 4p³ configuration mirrors nitrogen and phosphorus above it.

Frequently Asked Questions

Last updated: 2026-07-08 · Reviewed by Nham Vu

Arsenic Electron Configuration

Arsenic — Electron Configuration

Subshell Breakdown

Shell Fill Summary

Orbital Box Diagram

Quantum Numbers for All 33 Electrons

Identity

Physical Properties

Electronic Properties

Context & Uses

Summary

How it works

Use cases

Frequently Asked Questions

What is the electron configuration of arsenic?

What is the noble-gas shorthand for arsenic?

How many valence electrons does arsenic have?

Why does arsenic have three half-filled 4p orbitals?

What oxidation states does arsenic form?

What block and period is arsenic in?

How does arsenic's configuration compare to phosphorus?

Is arsenic a metal or nonmetal?