What is the electron configuration of boron?

Boron (B, Z=5) has the ground-state electron configuration 1s² 2s² 2p¹. Its five electrons fill the 1s and 2s subshells completely, with one electron in the 2p subshell.

What is the noble-gas shorthand for boron?

The condensed (noble-gas) notation is [He] 2s² 2p¹, where [He] represents the filled 1s² core shared with helium.

Why does boron form a +3 ion?

Boron loses its three valence electrons (2s² 2p¹) to achieve the stable [He] (1s²) noble-gas core, resulting in the B³⁺ ion.

What block and period is boron in?

Boron is in Period 2, Group 13 (IIIA), and belongs to the p-block of the periodic table. It is the first p-block element.

How many valence electrons does boron have?

Boron has 3 valence electrons: two in the 2s subshell and one in the 2p subshell.

Is boron a metal or nonmetal?

Boron is a metalloid (semimetal). It has some properties of metals and some of nonmetals, making it unique among Period 2 elements.

What is the 2p¹ orbital for boron?

The single 2p electron occupies one of the three available 2p orbitals (2px, 2py, or 2pz) with spin +½. The other two 2p orbitals remain empty.

Boron Electron Configuration

Name: Boron Electron Configuration
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Author: Nham Vu

Interactive reference for boron's electron configuration (1s² 2s² 2p¹), orbital diagram, and key atomic properties.

Z = 5 B Boron

Boron — Electron Configuration

Atomic number 5 · Metalloid · Period 2, Group 13 · p-block

1s² 2s² 2p¹ [He] 2s² 2p¹ 5 electrons 3 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 orbital, shell n=2	1	6	2p¹
Total		5

Full Configuration

1s² 2s² 2p¹

All subshells written explicitly.

Noble-Gas Shorthand

[He] 2s² 2p¹

[He] = 1s² (the filled helium core).

Shell Fill Summary

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

Shell 2 (n=2) — 2s² 2p¹ 3 / 8 electrons (37.5%)

Shell 2 can hold up to 8 electrons (2s + 2p). Boron uses 3 of those 8 slots — two in 2s and one in 2p.

Orbital Box Diagram

2 electrons (paired) — filled

1 electron (unpaired) — 2p_x only

Each box represents one orbital. Opposing arrows represent paired electrons with opposite spins (+½ and −½), satisfying the Pauli exclusion principle. Boron's single 2p electron is unpaired per Hund's rule — it occupies one 2p orbital alone before any pairing occurs.

Quantum Numbers

Electron #	n (shell)	l (subshell)	mₗ	mₛ (spin)	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

Summary

Interactive reference for boron's electron configuration (1s² 2s² 2p¹), orbital diagram, and key atomic properties.

How it works

The Aufbau principle fills orbitals from lowest to highest energy.
Boron's 5 electrons occupy three subshells: 1s (2 electrons), 2s (2 electrons), and 2p (1 electron).
The orbital box diagram shows each electron as an arrow following the Pauli exclusion principle and Hund's rule.
Noble-gas notation replaces the inner filled shells with the nearest noble gas in brackets: [He] 2s² 2p¹.
The interactive tabs let you explore the configuration, orbital diagram, and element data separately.

Use cases

Quick reference for chemistry homework or exam review.
Visualize orbital filling order and how the first p-block element begins.
Understand why boron commonly forms a +3 ion by losing its 2s² 2p¹ electrons.
Compare boron to other Period 2 elements and trace the filling of the 2p subshell.
Learn noble-gas shorthand notation with a clear worked example.
Teaching aid for introductory atomic structure and the p-block introduction.

Frequently Asked Questions

Last updated: 2026-06-18 · Reviewed by Nham Vu