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Ba 56

Barium (Ba)

alkaline-earth-metal
Period: 6 Group: 2 Block: s

Solid

Standard Atomic Weight

137.327 u

Electron configuration

[Xe] 6s2

Melting point

726.85 °C (1000 K)

Boiling point

1896.85 °C (2170 K)

Density

3620 kg/m³

Oxidation states

+1, +2

Electronegativity (Pauling)

0.89

Ionization energy (1st)

Discovery year

1808

Atomic radius

215 pm

Details

Name origin Greek: barys (heavy or dense).
Discovery country England
Discoverers Sir Humphrey Davy

Barium is a soft alkaline earth metal, below strontium and above radium in group 2. It is highly reactive, forms Ba²⁺ compounds almost exclusively, and is not found free in nature. Its most important minerals are barite, barium sulfate, and witherite, barium carbonate. The element is technologically significant less as a metal than through dense, insoluble, or optically useful compounds.

Barium is a metallic element, soft, and when pure is silvery white; it belongs to the alkaline earth group, chemically resembling calcium. The metal oxidizes very easily and should be kept under petroleum or other suitable oxygen-free liquids to exclude air. It is decomposed by water or alcohol.

Barium was first isolated by Sir Humphry Davy, an English chemist, in 1808 through the electrolysis of molten baryta (BaO). Barium is never found free in nature since it reacts with oxygen in the air, forming barium oxide (BaO), and with water, forming barium hydroxide (Ba(OH)2) and hydrogen gas (H2). Barium is most commonly found as the mineral barite (BaSO4) and witherite (BaCO3) and is primarily produced through the electrolysis of barium chloride (BaCl2).

From the Greek word barys, heavy. Baryta was distinguished from lime by Scheele in 1774; the element was discovered by Sir Humphrey Davy in 1808.

Read about Barium on Wikipedia

Images

Properties

Physical

Atomic radius (empirical) 215 pm
Covalent radius 215 pm
Van der Waals radius 268 pm
Metallic radius 198 pm
Density
Molar volume 0.039 L/mol
Phase at STP solid
Melting point 726.85 °C
Boiling point 1896.85 °C
Specific heat capacity 0.204 J/(g·K)
Molar heat capacity 28.07 J/(mol·K)
Crystal structure bcc

Chemical

Electronegativity (Pauling) 0.89
Electronegativity (Allen) 0.881
Electron affinity
Ionization energy (1st)
Ionization energy (2nd)
Ionization energy (3rd)
Ionization energy (4th)
Ionization energy (5th)
Oxidation states +1, +2
Valence electrons 2
Electron configuration
Electron configuration (semantic)

Thermodynamic

Heat of fusion 0.07939058 eV
Heat of vaporization 1.461367 eV
Heat of sublimation 1.865575 eV
Heat of atomization 1.865575 eV
Atomization enthalpy

Nuclear

Stable isotopes 6
Discovery year 1808

Abundance

Abundance (Earth's crust) 425 mg/kg
Abundance (ocean)

Reactivity

N/A

Crystal Structure

Lattice constant a 502 pm

Electronic Structure

Electrons per shell 2, 8, 18, 18, 8, 2

Identifiers

CAS number 7440-39-3
Term symbol
InChI InChI=1S/Ba
InChI Key DSAJWYNOEDNPEQ-UHFFFAOYSA-N

Electron Configuration Measured

Ion charge
Protons 56
Electrons 56
Charge Neutral
Configuration Ba: 6s²
Electron configuration
Measured
[Xe] 6s²
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s²
Orbital diagram
1s
2/2
2s
2/2
2p
6/6
3s
2/2
3p
6/6
4s
2/2
3d
10/10
4p
6/6
5s
2/2
4d
10/10
5p
6/6
6s
2/2
Total electrons: 56 Unpaired: 0

Atomic model

Protons 56
Neutrons 82
Electrons 56
Mass number 138
Stability Stable

Isotopes change neutron count, mass, and stability — not the electron configuration of a neutral atom.

Schematic atomic model, not to scale.

Atomic Fingerprint

Emission / Absorption Spectrum

25 / 50 (50 with intensity)
Measured
Emission Visible: 380–750 nm
Source: NIST Atomic Spectra Database Wavelengths in air

Isotope Distribution

13871.6980%13711.2320%1367.8540%1356.5920%1342.4170%Mass numberNatural abundance (%)
Mass numberAtomic mass (u)Natural abundanceHalf-life
134 Stable133.90450818 ± 0.00000032.4170%Stable
135 Stable134.90568838 ± 0.000000296.5920%Stable
136 Stable135.90457573 ± 0.000000297.8540%Stable
137 Stable136.90582714 ± 0.000000311.2320%Stable
138 Stable137.905247 ± 0.0000003171.6980%Stable
Measured

Phase / State

1 atm / 101.325 kPa
Solid 25 °C (298.15 K)

Reason: 701.9 °C below melting point (726.85 °C)

Melting point 726.85 °C
Boiling point 1896.85 °C
Below melting by 701.9 °C
0 K Current temperature: 25 °C 6000 K
Phase timeline

Schematic, not to scale

Solid
Liquid
Gas
Melting
Boiling
25°C
Solid
Liquid
Gas
Current

Phase transition points

Melting point Literature
726.85 °C
Boiling point Literature
1896.85 °C
Current phase Calculated
Solid

Transition energies

Heat of fusion Literature
0.07939058 eV

Energy required to melt 1 mol at melting point

Heat of vaporization Literature
1.461367 eV

Energy required to vaporize 1 mol at boiling point

Heat of sublimation Literature
1.865575 eV

Energy required to sublime 1 mol at sublimation point

Density

Reference density Literature
3620 kg/m³

At standard conditions

Current density Calculated
3620 kg/m³

At standard conditions

Atomic Spectra

Showing 10 of 56 Atomic Spectra. Sorted by ion charge (ascending).

Lines Holdings ?

IonChargeTotal linesTransition probabilitiesLevel designations
Ba I 0312109312
Ba II +111294112
Ba III +25355529
Ba IV +342342
Ba V +41350126
Ba VI +51380127
Ba VII +670070
Ba VIII +7141141141
Ba IX +8110110110
Ba X +9313131
NIST Lines Holdings →

Levels Holdings ?

IonChargeLevels
Ba I 0356
Ba II +1162
Ba III +2162
Ba IV +334
Ba V +452
Ba VI +550
Ba VII +632
Ba VIII +779
Ba IX +855
Ba X +930
NIST Levels Holdings →
56 Ba 137.327

Barium — Atomic Orbital Visualizer

[Xe]6s2
Energy levels 2 8 18 18 8 2
Oxidation states +1, +2
HOMO 6s n=6 · l=0 · m=0
Barium — Atomic Orbital Visualizer Preview
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56 Ba 137.327

Barium — Crystal Structure Visualizer

Body-Centered Cubic · Pearson cI2
Experimental
Pearson cI2
Coord. № 8
Packing 68.000%
Barium — Crystal Structure Visualizer Preview
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Ionic Radii

ChargeCoordinationSpinRadius
+26N/A135 pm
+27N/A138 pm
+28N/A142 pm
+29N/A147 pm
+210N/A152 pm
+211N/A157 pm
+212N/A161 pm

Compounds

Ba
137.330 u
Ba+2
137.330 u
Ba
132.906 u
Ba
139.911 u
Ba
138.909 u
Ba
130.907 u
Ba
137.905 u
Ba
125.911 u
Ba
136.906 u
Ba
134.906 u
Ba
140.914 u
Ba
141.916 u
Ba
127.908 u
Ba
129.906 u
Ba
131.905 u
Ba
133.905 u
Ba
135.905 u

Isotopes (5)

Mass numberAtomic mass (u)Natural abundanceHalf-lifeDecay mode
134 Stable133.90450818 ± 0.00000032.4170% ± 0.0180%Stable
stable
135 Stable134.90568838 ± 0.000000296.5920% ± 0.0120%Stable
stable
136 Stable135.90457573 ± 0.000000297.8540% ± 0.0240%Stable
stable
137 Stable136.90582714 ± 0.000000311.2320% ± 0.0240%Stable
stable
138 Stable137.905247 ± 0.0000003171.6980% ± 0.0420%Stable
stable
134 Stable
Atomic mass (u) 133.90450818 ± 0.0000003
Natural abundance 2.4170% ± 0.0180%
Half-life Stable
Decay mode
stable
135 Stable
Atomic mass (u) 134.90568838 ± 0.00000029
Natural abundance 6.5920% ± 0.0120%
Half-life Stable
Decay mode
stable
136 Stable
Atomic mass (u) 135.90457573 ± 0.00000029
Natural abundance 7.8540% ± 0.0240%
Half-life Stable
Decay mode
stable
137 Stable
Atomic mass (u) 136.90582714 ± 0.0000003
Natural abundance 11.2320% ± 0.0240%
Half-life Stable
Decay mode
stable
138 Stable
Atomic mass (u) 137.905247 ± 0.00000031
Natural abundance 71.6980% ± 0.0420%
Half-life Stable
Decay mode
stable

Spectral Lines

Showing 50 of 92 Spectral Lines. Only spectral lines with measured intensity are shown by default.

Wavelength (nm)IntensityIon stageTypeTransitionAccuracySource
392.686 nm25Ba IIIemission5p5.(2P*<3/2>).6s 2[3/2]* → 5p5.(2P*<3/2>).6p 2[1/2]MeasuredNIST
399.306 nm25Ba IIIemission5p5.(2P*<3/2>).6s 2[3/2]* → 5p5.(2P*<3/2>).6p 2[5/2]MeasuredNIST
381.3128 nm16Ba IIIemission5p5.(2P*<1/2>).6s 2[1/2]* → 5p5.(2P*<1/2>).4f 2[5/2]MeasuredNIST
469.7428 nm15Ba IIIemission5p5.(2P*<1/2>).5d 2[3/2]* → 5p5.(2P*<1/2>).6p 2[1/2]MeasuredNIST
448.1646 nm14Ba IIIemission5p5.(2P*<1/2>).5d 2[3/2]* → 5p5.(2P*<3/2>).6p 2[5/2]MeasuredNIST
610.1987 nm13Ba IIIemission5p5.(2P*<1/2>).5d 2[3/2]* → 5p5.(2P*<1/2>).4f 2[5/2]MeasuredNIST
389.6957 nm12Ba IIIemission5p5.(2P*<3/2>).5d 2[5/2]* → 5p5.(2P*<3/2>).4f 2[3/2]MeasuredNIST
392.723 nm10Ba IIIemission5p5.(2P*<3/2>).5d 2[5/2]* → 5p5.(2P*<3/2>).4f 2[9/2]MeasuredNIST
432.793 nm10Ba IIIemission5p5.(2P*<3/2>).6s 2[3/2]* → 5p5.(2P*<3/2>).6p 2[1/2]MeasuredNIST
482.0642 nm10Ba IIIemission5p5.(2P*<3/2>).5f 2[3/2] → 5p5.(2P*<3/2>).5g 2[5/2]*MeasuredNIST
485.0833 nm10Ba IIIemission5p5.(2P*<3/2>).5f 2[3/2] → 5p5.(2P*<3/2>).5g 2[5/2]*MeasuredNIST
496.4038 nm10Ba IIIemission5p5.(2P*<3/2>).5f 2[5/2] → 5p5.(2P*<3/2>).5g 2[7/2]*MeasuredNIST
504.9533 nm10Ba IIIemission5p5.(2P*<3/2>).5f 2[5/2] → 5p5.(2P*<3/2>).5g 2[7/2]*MeasuredNIST
509.7537 nm10Ba IIIemission5p5.(2P*<3/2>).5f 2[7/2] → 5p5.(2P*<3/2>).5g 2[9/2]*MeasuredNIST
513.4529 nm10Ba IIIemission5p5.(2P*<3/2>).5f 2[7/2] → 5p5.(2P*<3/2>).5g 2[9/2]*MeasuredNIST
599.7996 nm10Ba IIIemission5p5.(2P*<3/2>).7p 2[5/2] → 5p5.(2P*<3/2>).7d 2[7/2]*MeasuredNIST
637.7094 nm10Ba IIIemission5p5.(2P*<3/2>).7p 2[3/2] → 5p5.(2P*<3/2>).7d 2[5/2]*MeasuredNIST
638.3756 nm10Ba IIIemission5p5.(2P*<3/2>).7p 2[5/2] → 5p5.(2P*<3/2>).7d 2[7/2]*MeasuredNIST
438.5824 nm9Ba IIIemission5p5.(2P*<1/2>).5d 2[5/2]* → 5p5.(2P*<3/2>).6p 2[5/2]MeasuredNIST
464.6207 nm9Ba IIIemission5p5.(2P*<3/2>).5d 2[5/2]* → 5p5.(2P*<3/2>).4f 2[3/2]MeasuredNIST
542.699 nm9Ba IIIemission5p5.(2P*<1/2>).5d 2[5/2]* → 5p5.(2P*<3/2>).6p 2[5/2]MeasuredNIST
491.7171 nm8Ba IIIemission5p5.(2P*<1/2>).5f 2[7/2] → 5p5.(2P*<1/2>).5g 2[9/2]*MeasuredNIST
494.5436 nm8Ba IIIemission5p5.(2P*<1/2>).5f 2[5/2] → 5p5.(2P*<1/2>).5g 2[7/2]*MeasuredNIST
495.2914 nm8Ba IIIemission5p5.(2P*<1/2>).5f 2[5/2] → 5p5.(2P*<1/2>).5g 2[7/2]*MeasuredNIST
496.3235 nm8Ba IIIemission5p5.(2P*<1/2>).5f 2[7/2] → 5p5.(2P*<1/2>).5g 2[9/2]*MeasuredNIST
503.3498 nm8Ba IIIemission5p5.(2P*<3/2>).7p 2[5/2] → 5p5.(2P*<3/2>).5g 2[5/2]*MeasuredNIST
503.7341 nm8Ba IIIemission5p5.(2P*<1/2>).5d 2[3/2]* → 5p5.(2P*<1/2>).6p 2[1/2]MeasuredNIST
590.0288 nm8Ba IIIemission5p5.(2P*<3/2>).5f 2[9/2] → 5p5.(2P*<3/2>).7d 2[7/2]*MeasuredNIST
601.6412 nm8Ba IIIemission5p5.(2P*<1/2>).5d 2[3/2]* → 5p5.(2P*<1/2>).6p 2[3/2]MeasuredNIST
603.6589 nm8Ba IIIemission5p5.(2P*<3/2>).5f 2[5/2] → 5p5.(2P*<3/2>).7d 2[7/2]*MeasuredNIST
607.7807 nm8Ba IIIemission5p5.(2P*<3/2>).6s 2[3/2]* → 5p5.(2P*<3/2>).4f 2[3/2]MeasuredNIST
627.0084 nm8Ba IIIemission5p5.(2P*<3/2>).7p 2[3/2] → 5p5.(2P*<3/2>).7d 2[5/2]*MeasuredNIST
652.6166 nm8Ba IIIemission5p5.(2P*<3/2>).7p 2[5/2] → 5p5.(2P*<3/2>).8s 2[3/2]*MeasuredNIST
709.5497 nm8Ba IIIemission5p5.(2P*<3/2>).6s 2[3/2]* → 5p5.(2P*<3/2>).4f 2[3/2]MeasuredNIST
519.6426 nm7Ba IIIemission5p5.(2P*<3/2>).7p 2[5/2] → 5p5.(2P*<3/2>).5g 2[7/2]*MeasuredNIST
552.8138 nm7Ba IIIemission5p5.(2P*<1/2>).5d 2[3/2]* → 5p5.(2P*<3/2>).6p 2[1/2]MeasuredNIST
574.0413 nm7Ba IIIemission5p5.(2P*<3/2>).5f 2[3/2] → 5p5.(2P*<3/2>).7d 2[7/2]*MeasuredNIST
579.8254 nm7Ba IIIemission5p5.(2P*<3/2>).5f 2[5/2] → 5p5.(2P*<3/2>).7d 2[5/2]*MeasuredNIST
585.9192 nm7Ba IIIemission5p5.(2P*<3/2>).7p 2[5/2] → 5p5.(2P*<3/2>).7d 2[5/2]*MeasuredNIST
588.1879 nm7Ba IIIemission5p5.(2P*<3/2>).5f 2[9/2] → 5p5.(2P*<3/2>).7d 2[7/2]*MeasuredNIST
598.3721 nm7Ba IIIemission5p5.(2P*<3/2>).7p 2[1/2] → 5p5.(2P*<3/2>).7d 2[1/2]*MeasuredNIST
658.3333 nm7Ba IIIemission5p5.(2P*<3/2>).7p 2[3/2] → 5p5.(2P*<3/2>).7d 2[3/2]*MeasuredNIST
565.8601 nm6Ba IIIemission5p5.(2P*<1/2>).5d 2[5/2]* → 5p5.(2P*<3/2>).4f 2[7/2]MeasuredNIST
569.7415 nm6Ba IIIemission5p5.(2P*<3/2>).5f 2[3/2] → 5p5.(2P*<3/2>).7d 2[3/2]*MeasuredNIST
571.6614 nm6Ba IIIemission5p5.(2P*<3/2>).7p 2[1/2] → 5p5.(2P*<3/2>).7d 2[3/2]*MeasuredNIST
572.6169 nm6Ba IIIemission5p5.(2P*<3/2>).7p 2[3/2] → 5p5.(2P*<3/2>).7d 2[3/2]*MeasuredNIST
581.3545 nm6Ba IIIemission5p5.(2P*<3/2>).5f 2[3/2] → 5p5.(2P*<3/2>).7d 2[1/2]*MeasuredNIST
607.6665 nm6Ba IIIemission5p5.(2P*<3/2>).5f 2[7/2] → 5p5.(2P*<3/2>).7d 2[5/2]*MeasuredNIST
613.1372 nm6Ba IIIemission5p5.(2P*<3/2>).7p 2[5/2] → 5p5.(2P*<3/2>).7d 2[1/2]*MeasuredNIST
640.614 nm6Ba IIIemission5p5.(2P*<3/2>).7p 2[1/2] → 5p5.(2P*<3/2>).7d 2[3/2]*MeasuredNIST

Extended Properties

Covalent Radii (Extended)

Covalent radius (Pyykkö)  
Covalent radius (Pyykkö, double)  
Covalent radius (Pyykkö, triple)  
Covalent radius (Bragg)  

Van der Waals Radii

Truhlar  
Batsanov  
Alvarez  
UFF  
MM3  

Atomic & Metallic Radii

Atomic radius (Rahm)  
Metallic radius (C12)  

Numbering Scales

Mendeleev
Pettifor
Glawe

Electronegativity Scales

Ghosh
Miedema
Gunnarsson–Lundqvist
Robles–Bartolotti

Polarizability & Dispersion

Dipole polarizability  
Dipole polarizability (unc.)  
C₆ (Gould–Bučko)  

Miedema Parameters

Miedema molar volume  
Miedema electron density

Supply Risk & Economics

Production concentration
Relative supply risk
Reserve distribution
Political stability (top producer)
Political stability (top reserve)

Phase Transitions & Allotropes

Melting point1000.15 K
Boiling point2118.15 K

Oxidation State Categories

+1 extended
+2 main

Advanced Reference Data

Screening Constants (12)
nOrbitalσ
1s1.1139
2p4.1904
2s14.7532
3d13.9757
3p18.6836
3s18.8444
4d32.216
4p29.1968
4s28.08
5p41.1995
Crystal Radii Detail (7)
ChargeCNSpinrcrystal (pm)Origin
2VI149
2VII152calculated,
2VIII156
2IX161
2X166
2XI171
2XII175calculated,
Isotope Decay Modes (55)
IsotopeModeIntensity
113p—
113A—
114B+100%
114B+p20%
114A0.9%
11412C0%
115B+100%
115B+p15%
116B+100%
116B+p3%
X‑ray Scattering Factors (508)
Energy (eV)f₁f₂
10—0.10258
10.1617—0.10761
10.3261—0.11287
10.4931—0.1184
10.6628—0.1242
10.8353—0.13028
11.0106—0.13666
11.1886—0.14335
11.3696—0.15037
11.5535—0.15773

Additional Data

Sources

Sources of this element.

It is found only in combination with other elements, chiefly with sulfate and carbonate and is prepared by electrolysis of the chloride.

References (1)

References

(9)
2 Atomic Mass Data Center (AMDC), International Atomic Energy Agency (IAEA)
Ba

The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.

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3 IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW)
Barium

Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.

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4 IUPAC Periodic Table of the Elements and Isotopes (IPTEI)

The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.

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License note: Copyright (c) 2020 International Union of Pure and Applied Chemistry. The International Union of Pure and Applied Chemistry (IUPAC) contribution within Pubchem is provided under a CC-BY-NC-ND 4.0 license, unless otherwise stated.
5 Jefferson Lab, U.S. Department of Energy
Barium

Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/

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License note: Please see citation and linking information: https://education.jlab.org/faq/index.html
6 Los Alamos National Laboratory, U.S. Department of Energy
Barium

The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.

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7 NIST Physical Measurement Laboratory
Barium

The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database

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8 PubChem Elements
Barium

This section provides all form of data related to element Barium.

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9 PubChem Elements
Barium

The element property data was retrieved from publications.

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Last updated:

Data verified:

Content is reviewed against latest scientific data.