5 B Boron 10.81 u

Boron

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Period
2
Group
13
Block
p-block
Phase (STP)
Solid

Boron is a metalloid essential for plant growth and used in glass and ceramics. Its compounds, such as borax, have been used for thousands of years.

Appearance: Black-brown

About Boron

A metalloid straddling the boundary between metals and nonmetals, boron carries atomic number 5 and an atomic mass of 10.81. In elemental form it appears black-brown and is hard and refractory, melting near 2349 K. Three valence electrons ([He] 2s2 2p1) and an electronegativity of 2.04 favor covalent bonding, and its first ionization energy is 800.6 kJ/mol. Joseph Louis Gay-Lussac helped isolate the element in 1808, though boron compounds such as borax had already been used for thousands of years. Boron is essential to plant growth and is incorporated into glass and ceramics. It belongs to group 13, period 2.

Physical Properties

Atomic Mass 10.81 u
Density 2.34 g/cm³
Melting Point 2075.8 °C
Boiling Point 3926.8 °C
Phase at STP Solid
Atomic Radius 87.0 pm

Electronic Properties

Electronegativity 2.04
Ionization Energy 800.6 eV
Electron Affinity 26.7 eV
Valence Electrons 3

Electron Configuration

Configuration [He] 2s² 2p¹

Electron Shell Configuration

Boron electron shell configuration B 2e⁻ 3e⁻
Electron shell structure of Boron — electrons per shell.
Shell Electrons
1 (K) 2
2 (L) 3

Position in Periodic Table

Boron position in the periodic table B

Discovery

Discovered by: Joseph Louis Gay-Lussac
Year: 1808

Block & Period

Block

s p d f

Period

1 2 3 4 5 6 7

Periodic Table

Lanthanides Actinides

Reactions Involving B

Boron Trifluoride and Ammonia (Lewis Acid-Base)

BF₃ + NH₃ → BF₃·NH₃

Acid-Base

Positron Emission of Carbon-11

¹¹C → ¹¹B + e⁺ + νₑ

Nuclear

Compounds Containing Boron

Boric Acid

H₃BO₃

Boron Nitride

BN

Boron Trichloride

BCl₃

Boron Trifluoride

BF₃

Boron Trioxide

B₂O₃

Diborane

B₂H₆

Sodium Borohydride

NaBH₄

Sodium Borohydride in NaOH

NaBH₄/NaOH

Sodium Perborate

NaBO₃

Sodium Tetraborate

Na₂B₄O₇

More Metalloid

14 Si Silicon 32 Ge Germanium 33 As Arsenic 51 Sb Antimony 52 Te Tellurium

Frequently Asked Questions

What is Boron?
Boron (B) is a chemical element with atomic number 5. It is a solid at standard temperature and pressure, classified as a metalloid.
What are the key properties of Boron?
Boron has an atomic mass of 10.81 u, density of 2.34 g/cm³, melting point of 2075.8°C, boiling point of 3926.8°C.
What is the electron configuration of Boron?
The electron configuration of Boron is [He] 2s2 2p1. It is in the p-block of the periodic table.
Who discovered Boron?
Boron was discovered by Joseph Louis Gay-Lussac in 1808.
What is the electronegativity of Boron?
Boron has an electronegativity of 2.04 on the Pauling scale.