Boron (B)
Metalloid · p-block · period 2 · group 13
Hard, brittle, lustrous black-brown metalloid.
Boron (symbol B) is chemical element number 5, a metalloid in group 13, period 2 of the periodic table. Its standard atomic weight is 10.81 and its electron configuration is [He] 2s2 2p1. At room temperature it is a solid. Absorbs neutrons strongly, so it is used in nuclear reactor control rods.
Properties
| Atomic number | 5 |
|---|---|
| Atomic mass | 10.81 |
| Category | Metalloid |
| Block | p-block |
| Group · Period | 13 · 2 |
| Electron configuration | [He] 2s2 2p1 |
| Electrons per shell | 2, 3 |
| State at 25 °C | solid |
| Melting point | 2349 K |
| Boiling point | 4200 K |
| Density | 2.34 g/cm³ |
| Electronegativity (Pauling) | 2.04 |
| Radioactive | No |
| Origin | primordial |
| Discovered | 1808 · Davy; Gay-Lussac & Thénard |
Key facts about Boron
- Absorbs neutrons strongly, so it is used in nuclear reactor control rods.
- Borax and boric acid have been known as cleaning agents for centuries.
- Essential in tiny amounts for healthy plant growth.
- Adds strength and heat resistance to borosilicate glass (Pyrex).
What Boron is used for
Borosilicate glass, detergents, ceramics, fibreglass, neutron shielding.
Where it sits in the periodic table
Boron is in group 13, period 2, of the p-block. Its electron configuration [He] 2s2 2p1 means its outermost shell holds 3 electrons, which is what places it here and explains much of its chemistry. See Boron on the interactive table →
Boron — frequently asked questions
What is Boron used for?
Borosilicate glass, detergents, ceramics, fibreglass, neutron shielding.
Is Boron radioactive?
No. Boron has at least one stable isotope and is not radioactive.
What is the electron configuration of Boron?
Boron has the electron configuration [He] 2s2 2p1, which is 2, 3 electrons per shell.
What group and period is Boron in?
Boron is in group 13, period 2, in the p-block. Its outer shell holds 3 electrons.
Who discovered Boron?
Boron was discovered in 1808 by Davy; Gay-Lussac & Thénard.