Chemical element · Atomic number 5
Boron
Boron in the periodic table: atomic number 5, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Metalloid
solid
10.81 u
Documented element samplePolycrystalline chunks of rhombohedral beta boron weighing about 25 grams in total.
Image credit: James L Marshall
Auto-oriented, limited to 1600 × 1200 pixels and re-encoded as WebP; the subject was not altered.
Atomic classification
Shell occupancy
Boron in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 3 electrons
- Electron configuration
- [He]2s2 2p1
- Electrons per shell
- 2 · 3
- Group
- 13
- Period
- 2
- Block
- P
- Element category
- Metalloid
Physical and chemical properties
- Atomic mass
- 10.81 u
- Standard state
- solid
- Density
- 2.37 g/cm³
- Melting point
- 2,348 K
- Boiling point
- 4,273 K
- Electronegativity
- 2.04 (Pauling)
- First ionisation energy
- 8.298 eV
- Oxidation states
- +3
- Discovery
- 1808
Safety and periodic classification
Safety
Safe handling cannot be inferred from Boron's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Boron is in period 2, group 13 and the P block. Its direct neighbours by atomic number are Beryllium and Carbon. The recorded Pauling electronegativity is 2.04. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.
Where Boron sits among the 118 elements
The table compares the reported values for Boron with every other element that carries the same value in the snapshot. A rank is not a judgement, it is orientation: it says how unusual this value is across the periodic table.
| Value | Boron | Position in the data set |
|---|---|---|
| Melting point | 2,348 K | Rank 12 of 103 elements with a reported value. Highest: Carbon. |
| Boiling point | 4,273 K | Rank 14 of 93 elements with a reported value. Highest: Rhenium. |
| Density | 2.37 g/cm³ | Rank 73 of 96 elements with a reported value. Highest: Osmium. |
| Electronegativity (Pauling) | 2.04 | Rank 28 of 95 elements with a reported value. Highest: Fluorine. |
| Ionisation energy | 8.298 eV | Rank 32 of 102 elements with a reported value. Highest: Helium. |
All values and ranks come from the PubChem Periodic Table snapshot, retrieved on 2026-07-15. Elements without a reported value are excluded, so the population differs per row.
The neighbours of Boron in the periodic table
- Place in the table
- Group 13, period 2, P block. Classified as metalloid, solid at standard conditions.
- Direct neighbours
- Atomic number 5. Preceded by Beryllium, followed by Carbon.
- Same group
- Same number of outer electrons, and therefore similar reactivity to Aluminum, Gallium, Indium, Thallium, Nihonium.
- Discovery
- Recorded in the snapshot as: 1808. Who, where and under what circumstances is not part of that record, so this page carries the sourced year and no discovery narrative.
- Oxidation states
- +3. They follow from the electron configuration [He]2s2 2p1 and indicate which compounds to expect.
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