Boron Element Information, Facts, Properties, Trends, Uses, Comparison with other elements
Boron is a Metalloid chemical element with symbol B and atomic number 5. Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in both the Solar system and the Earth's crust. Boron is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals.
It belongs to group 13 of the periodic table having trivial name triels, icosagens. You can also download Printable Periodic Table of Elements Flashcards for Boron in a PDF format.
Boron Facts
Read key information and facts about element Boron
| Name | Boron |
| Atomic Number | 5 |
| Atomic Symbol | B |
| Atomic Weight | 10.811 |
| Phase | Solid |
| Color | Black |
| Appearance | black-brown |
| Classification | Metalloid |
| Natural Occurance | Primordial |
| Group in Periodic Table | 13 |
| Group Name | boron family |
| Period in Periodic Table | period 2 |
| Block in Periodic Table | p-block |
| Electronic Configuration | [He] 2s2 2p1 |
| Electronic Shell Structure (Electrons per shell) | 2, 3 |
| Melting Point | 2348 K |
| Boiling Point | 4273 K |
| CAS Number | CAS7440-42-8 |
How to Locate Boron on Periodic Table
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 5 to find Boron on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Boron on periodic table look for cross section of group 13 and period 2 in the modern periodic table.
Boron History
The element Boron was discovered by L. Gay-Lussac and L.J. Thénard in year 1808 in France and United Kingdom. Boron was first isolated by H. Davy in 1808. Boron derived its name from borax, a mineral.
| Discovered By | L. Gay-Lussac and L.J. Thénard |
| Discovery Date | 1808 in France and United Kingdom |
| First Isolation | 1808 |
| Isolated by | H. Davy |
Radical boracique appears on the list of elements in Lavoisier's Traité Élémentaire de Chimie from 1789. On June 21, 1808, Lussac and Thénard announced a new element in sedative salt, Davy announced the isolation of a new substance from boracic acid on June 30.
Boron Uses
Boron is used in pyrotechnics. When burned, it gives off a green color in the flame. Mostly Boron is used in boric acid and borax. It can also be found in antiseptics, washing chemicals, ceramic glazes, and eye drops.
Boron Presence: Abundance in Nature and Around Us
The table below shows the abundance of Boron in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
| ppb by weight (1ppb =10^-7 %) | ppb by atoms (1ppb =10^-7 %) | |
|---|---|---|
| Abundance in Universe | 1 | 0.1 |
| Abundance in Sun | 2 | 0.2 |
| Abundance in Meteorites | 1600 | 3000 |
| Abundance in Earth's Crust | 8700 | 17000 |
| Abundance in Oceans | 4440 | 2500 |
| Abundance in Humans | 700 | 410 |
Crystal Structure of Boron
The solid state structure of Boron is Simple Trigonal.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
Unit Cell Parameters
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
| a | b | c |
|---|---|---|
| 506 pm | 506 pm | 506 pm |
and the angles between them Lattice Angles (alpha, beta and gamma).
| alpha | beta | gamma |
|---|---|---|
| 1.01334 | 1.01334 | 1.01334 |
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
| Space Group Name | R_ 3m |
| Space Group Number | 166 |
| Crystal Structure | Simple Trigonal |
| Number of atoms per unit cell |
The number of atoms per unit cell in a simple cubic, face-centered cubic and body-centred cubic are 1,4,2 respectively.
Boron Atomic and Orbital Properties
Boron atoms have 5 electrons and the electronic shell structure is [2, 3] with Atomic Term Symbol (Quantum Numbers) 2P1/2.
| Atomic Number | 5 |
| Number of Electrons (with no charge) | 5 |
| Number of Protons | 5 |
| Mass Number | 11 |
| Number of Neutrons | 6 |
| Shell structure (Electrons per energy level) | 2, 3 |
| Electron Configuration | [He] 2s2 2p1 |
| Valence Electrons | 2s2 2p1 |
| Valence (Valency) | 3 |
| Main Oxidation States | 3 |
| Oxidation States | -5, -1, 0, 1, 2, 3 |
| Atomic Term Symbol (Quantum Numbers) | 2P1/2 |
Bohr Atomic Model of Boron - Electrons per energy level
| n | s | p | d | f |
|---|
Ground State Electronic Configuration of Boron - neutral Boron atom
Abbreviated electronic configuration of Boron
The ground state abbreviated electronic configuration of Neutral Boron atom is [He] 2s2 2p1. The portion of Boron configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [He]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 2s2 2p1, electrons in the outermost shell that determine the chemical properties of the element.
Unabbreviated electronic configuration of neutral Boron
Complete ground state electronic configuration for the Boron atom, Unabbreviated electronic configuration
1s2 2s2 2p1
Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.
As per the Aufbau principle the electrons will occupy the orbitals having lower energies before occupying higher energy orbitals. According to this principle, electrons are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
The Pauli exclusion principle states that a maximum of two electrons, each having opposite spins, can fit in an orbital.
Hund's rule states that every orbital in a given subshell is singly occupied by electrons before a second electron is filled in an orbital.
Atomic Structure of Boron
Boron atomic radius is 87 pm, while it's covalent radius is 82 pm.
| Atomic Radius Calculated | 87 pm(0.87 Å) |
| Atomic Radius Empirical | 85 pm (0.85 Å) |
| Atomic Volume | 4.3947 cm3/mol |
| Covalent Radius | 82 pm (0.82 Å) |
| Van der Waals Radius | 192 pm |
| Neutron Cross Section | 755 |
| Neutron Mass Absorption | 2.4 |
Spectral Lines of Boron - Atomic Spectrum of Boron
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules.
Spectral lines are the result of interaction between a quantum system and a single photon. A spectral line may be observed either as an emission line or an absorption line.
Spectral lines are highly atom-specific, and can be used to identify the chemical composition of any medium. Several elements, including helium, thallium, and caesium, were discovered by spectroscopic means. They are widely used to determine the physical conditions of stars and other celestial bodies that cannot be analyzed by other means.
Emission spectrum of Boron
Emission spectrum of Boron is not available
Absorption spectrum of Boron
Boron Chemical Properties: Boron Ionization Energies and electron affinity
The electron affinity of Boron is 26.7 kJ/mol.
| Valence | 3 |
| Electronegativity | 2.04 |
| ElectronAffinity | 26.7 kJ/mol |
Ionization Energy of Boron
Ionization energy is the amount of energy required to remove an electron from an atom or molecule.in chemistry, this energy is expresed in kilocalories per mole (kcal/mol) or kilojoules per mole (kJ/mol).
Refer to table below for Ionization energies of Boron
| Ionization energy number | Enthalpy - kJ/mol |
|---|---|
| 1st | 800.6 |
| 2nd | 2427.1 |
| 3rd | 3659.7 |
| 4th | 25025.8 |
| 5th | 32826.7 |
Boron Physical Properties
Refer to below table for Boron Physical Properties
| Density | 2.46 g/cm3(when liquid at m.p density is $2.08 g/cm3) |
| Molar Volume | 4.3947 cm3/mol |
Elastic Properties
| Young Modulus | - |
| Shear Modulus | - |
| Bulk Modulus | 320 GPa |
| Poisson Ratio | - |
Hardness of Boron - Tests to Measure of Hardness of Element
| Mohs Hardness | 9.3 MPa |
| Vickers Hardness | 49000 MPa |
| Brinell Hardness | - |
Boron Electrical Properties
Electrical resistivity measures element's electrical resistance or how strongly it resists electric current.The SI unit of electrical resistivity is the ohm-metre (Ω⋅m). While Electrical conductivity is the reciprocal of electrical resistivity. It represents a element's ability to conduct electric current. The SI unit of electrical conductivity is siemens per metre (S/m).
Boron is a Insulator. Refer to table below for the Electrical properties of Boron
| Electrical conductors | Insulator |
| Electrical Conductivity | 0.0001 S/m |
| Resistivity | 10000 m Ω |
| Superconducting Point | - |
Boron Heat and Conduction Properties
| Thermal Conductivity | 27 W/(m K) |
| Thermal Expansion | 0.000006 /K |
Boron Magnetic Properties
| Magnetic Type | Diamagnetic |
| Curie Point | - |
| Mass Magnetic Susceptibility | -8.7e-9 m3/kg |
| Molar Magnetic Susceptibility | -9.41e-11 m3/mol |
| Volume Magnetic Susceptibility | -0.0000214 |
Optical Properties of Boron
| Refractive Index | - |
Acoustic Properties of Boron
| Speed of Sound | 16200 m/s |
Boron Thermal Properties - Enthalpies and thermodynamics
Refer to table below for Thermal properties of Boron
| Melting Point | 2348 K(2074.85 °C, 3766.730 °F) |
| Boiling Point | 4273 K(3999.85 °C, 7231.730 °F) |
| Critical Temperature | - |
| Superconducting Point | - |
Enthalpies of Boron
| Heat of Fusion | 50 kJ/mol |
| Heat of Vaporization | 507 kJ/mol |
| Heat of Combustion | - |
Boron Isotopes - Nuclear Properties of Boron
Boron has 14 isotopes, with between 6 and 19 nucleons. Boron has 2 stable naturally occuring isotopes.
Isotopes of Boron - Naturally occurring stable Isotopes: 10B, 11B.
| Isotope | Z | N | Isotope Mass | % Abundance | T half | Decay Mode |
|---|---|---|---|---|---|---|
| 6B | 5 | 1 | 6 | Synthetic | ||
| 7B | 5 | 2 | 7 | Synthetic | ||
| 8B | 5 | 3 | 8 | Synthetic | ||
| 9B | 5 | 4 | 9 | Synthetic | ||
| 10B | 5 | 5 | 10 | 19.9% | Stable | N/A |
| 11B | 5 | 6 | 11 | 80.1% | Stable | |
| 12B | 5 | 7 | 12 | Synthetic | ||
| 13B | 5 | 8 | 13 | Synthetic | ||
| 14B | 5 | 9 | 14 | Synthetic | ||
| 15B | 5 | 10 | 15 | Synthetic | ||
| 16B | 5 | 11 | 16 | Synthetic | ||
| 17B | 5 | 12 | 17 | Synthetic | ||
| 18B | 5 | 13 | 18 | Synthetic | ||
| 19B | 5 | 14 | 19 | Synthetic |
Regulatory and Health - Health and Safety Parameters and Guidelines
The United States Department of Transportation (DOT) identifies hazard class of all dangerous elements/goods/commodities either by its class (or division) number or name. The DOT has divided these materials into nine different categories, known as Hazard Classes.
NFPA 704 is a Standard System for the Identification of the Hazards of Materials for Emergency Response. NFPA is a standard maintained by the US based National Fire Protection Association.
The health (blue), flammability (red), and reactivity (yellow) rating all use a numbering scale ranging from 0 to 4. A value of zero means that the element poses no hazard; a rating of four indicates extreme danger.
| NFPA Fire Rating | 3 | Flash Points below 37.8°C (100°F) |
| NFPA Health Rating | 2 | Flash Points Above 37.8°C (100°F) not exceeding 93.3°C (200°F) |
| NFPA Reactivity Rating | 0 | Will not burn |
| NFPA Hazards |
| Autoignition Point | - |
| Flashpoint | - |
Database Search
List of unique identifiers to search the element in various chemical registry databases
| Database | Identifier number |
|---|---|
| CAS Number - Chemical Abstracts Service (CAS) | CAS7440-42-8 |
| RTECS Number | RTECSED7350000 |
| CID Number | CID5462311 |
| Gmelin Number | - |
| NSC Number | - |
Compare Boron with other elements
Compare Boron with Group 13, Period 2 and Metalloid elements of the periodic table.
Compare Boron with all Group 13 elements
Compare Boron with all Period 2 elements
Compare Boron with all Metalloid elements
Frequently Asked Questions (FAQ)
Find the answers to the most frequently asked questions about Boron