Boron (B)

Element 5 · Metalloid · Solid at 25 °C · Group 13, Period 2

Boron gives borosilicate glass its resistance to heat, which is why labware and oven-safe glassware survive the flame.

On the periodic table, boron sits in group 13 — the boron group — in period 2. It is one of 6 elements classified as a metalloid, and at room temperature (25 °C) it is a solid.

Metalloids line the zig-zag “staircase” between the metals and nonmetals and behave a bit like both: they look metallic but are brittle and conduct electricity only moderately well. That in-between conductivity — a semiconductor's — is exactly what modern electronics is built on.

Properties of boron

Properties of Boron
Atomic number (Z)	5
Symbol	B
Atomic mass	10.81
Category	Metalloid
Group	13
Period	2
Block	p-block
Metal / nonmetal	Metalloid
State at 25 °C	Solid
Electron configuration	[He] 2s2 2p1
Electronegativity (Pauling)	2.04
Melting point	2,076 °C (2,349.15 K / 3,768.8 °F)
Boiling point	3,927 °C (4,200.15 K / 7,100.6 °F)
Density	2.34 g/cm³

Position in the periodic table

Boron shares group 13 — the boron group with Aluminium (Al), Gallium (Ga), Indium (In), Thallium (Tl), Nihonium (Nh). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.

Physical properties

Boron melts at 2,076 °C (2,349.15 K / 3,768.8 °F) and boils at 3,927 °C (4,200.15 K / 7,100.6 °F), giving it a liquid range of about 1,851 °C at standard pressure.

Its density is 2.34 g/cm³.