510.81BBoron
Boron (B) — element 5metalloid · group 13, period 2
Boron is a chemical element with the symbol B and atomic number 5. It is a metalloid in group 13, period 2 of the periodic table (the p-block), with a standard atomic mass of 10.81 u. At room temperature (25 °C) boron is a solid.
💡 Known for: Used in heat-resistant borosilicate glass, in borax detergents and in neutron-absorbing reactor control rods.
# Boron properties
| Symbol | B |
|---|---|
| Atomic number | 5 |
| Atomic mass | 10.81 u |
| Category | metalloid |
| Group | 13 |
| Period | 2 |
| Block | p-block |
| Electron configuration | [He] 2s² 2p¹ |
| Full configuration | 1s² 2s² 2p¹ |
| Electrons per shell | 2, 3 |
| Protons / electrons | 5 / 5 |
| State at 25 °C | solid |
| Melting point | 2349 K (2075.8 °C, 3768.5 °F) |
| Boiling point | 4200 K (3926.8 °C, 7100.3 °F) |
| Density | 2.34 g/cm³ |
| Electronegativity (Pauling) | 2.04 |
| First ionization energy | 8.298 eV |
| Atomic radius | 87 pm |
| Discovered | 1808 |
# Electron configuration of boron
The electron configuration of boron is [He] 2s² 2p¹, written out in full as 1s² 2s² 2p¹. Its 5 electrons fill 2 shells as 2, 3, so the outermost shell holds 3 electrons. As a group 13 element, boron has 3 valence electrons.
# Related elements
BeBerylliumprevious elementCCarbonnext elementAlAluminiumgroup 13GaGalliumgroup 13InIndiumgroup 13TlThalliumgroup 13NhNihoniumgroup 13SiSiliconmetalloidGeGermaniummetalloidAsArsenicmetalloidSbAntimonymetalloidTeTelluriummetalloid
# Boron FAQ
What is the atomic number of boron?
The atomic number of boron is 5: every boron atom has 5 protons in its nucleus. Its symbol is B.
What is the atomic mass of boron?
The standard atomic mass of boron is 10.81 u.
What is the electron configuration of boron?
Boron's electron configuration is [He] 2s² 2p¹ (1s² 2s² 2p¹), with 2, 3 electrons per shell.
Is boron a metal?
No. Boron is a metalloid, with properties between those of metals and nonmetals.
What is the melting point of boron?
Boron melts at 2349 K (2075.8 °C, 3768.5 °F) and boils at 4200 K (3926.8 °C, 7100.3 °F).
What is boron used for / known for?
Used in heat-resistant borosilicate glass, in borax detergents and in neutron-absorbing reactor control rods.