Barium

Bariumo Essential data : names, symbol, atomic number, and atomic weight; block, period, and group in

periodic table; description; standard state; registry number; and isolationo History : meaning of name; discovery; and history of the elemento Uses o Find a property

Barium around uso Geology : Abundance of elements in the universe; the sun; meteorites; Earth's crust; oceans; and

streamso Biology : Abundance in humans; biological role; and health hazards)

Chemistry and compoundso Compounds : halides, oxides, sulfides, hydrides, and complexes; lattice energies; and reduction

potentialso Reactions of barium : reactions of barium with air; water; halogens; acids; and baseso Electronegativities : Pauling; Sanderson; Allred Rochow; Mulliken-Jaffe; and Alleno Bond enthalpies  of diatomic specieso Lattice energies

Element propertieso Physics properties : Boiling point; melting point; density; molar volume; thermal conductivity; and

electrical resistivity; bulk modulus; critical temperature; superconductivity temperature; hardness (mineralogical, Brinell, and Vickers); linear expansion coefficient; Poisson's ratio; reflectivity; refractive index; rigidity modulus; Young's modulus; velocity of sound

o Crystal structure o Thermochemistry : enthalpies of atomization, fusion, and vaporization; thermodynamic propertieso Pictures

Atom propertieso Electron shell properties : Electronic configuration; term symbol; electron affinity; ionization

energies; and atomic spectrao Atom sizes : atomic radius; Shannon and Pauling ionic radii; covalent radius; metallic radius; element

bond length; and Van der Waals radiuso Atomic orbital properties : effective nuclear charge; electron binding energies; and valence orbital

radii maxima

Nuclear propertieso Isotopes : isotope abundances; radioactive isotopes; isotope masses; nuclear spins; and nuclear

magnetic momento NMR properties : frequencies; isotopes; magnetogyric ratios; quadrupole moments; receptivities; and

relative sensitivities

Barium: the essentials

Brief description: barium is a metallic element, soft, and when pure is silvery white like lead. The metal oxidises very easily and it reacts with water or alcohol. Barium is one of the alkaline-earth metals. Small amounts of barium compounds are used in paints and glasses.

The result of adding different metal salts to a burning reaction mixture of potassium chlorate and sucrose. The red colour originates from strontium sulphate. The

orange/yellow colour originates from sodium chloride. The green colour originates from barium chlorate and the blue colour originates from copper (I) chloride. The

lilac colour that should be evident from the potassium chlorate is washed out by the other colours, all of which are more intense (only to be demonstrated by a

professionally qualified chemist following a legally satisfactory hazard asessment). Improperly done, this reaction is dangerous!

Barium salts impart green colours to flames. The picture above shows the colour arising from adding barium chlorate (BaClO3) to a burning mixture. Do not attempt this reaction unless are a professionally qualified chemist and you have carried out a legally satisfactory hazard assessment.

Table: basic information about and classifications of barium.

Name : Barium Symbol : Ba Atomic number : 56 Atomic weight : 137.327 (7) Standard state : solid at 298 K CAS Registry ID : 7440-39-3

Group in periodic table : 2 Group name : Alkaline earth metal Period in periodic table : 6 Block in periodic table : s-block Colour : silvery white Classification : Metallic

Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.

Isolation

Isolation: barium metal is available commercially and there is normally no need to make it in the laboratory. Commercially, it is made on small scale by the electrolysis of molten barium chloride, BaCl2.

cathode: Ba2+(l) + 2e- → Ba

anode: Cl-(l) → 1/2Cl2 (g) + e-

Barium metal can also be islated from the reduction of barium oxide, BaO, with aluminium.

6BaO + 2Al→ 3Ba + Ba3Al2O6

Barium: historical information

Barium was discovered by Sir Humphrey Davy at 1808 in England.Origin of name: from the Greek word "barys" meaning "heavy".Further information on origin of name and discovery dates

Baryta (barium oxide, BaO) was distinguished from lime (calcium oxide, CaO) by Scheele in 1774. Elemental barium was isolated by Sir Humphrey Davy in 1808 who electrolysed molten baryta.

Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms. Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in thePhilosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy. The symbol used by Dalton for barium is shown below. [See History of Chemistry, Sir Edward Thorpe, volume 1, Watts & Co, London, 1914.]

Barium: uses

The following uses for barium are gathered from a number of sources as well as from anecdotal comments. I'd be delighted to receive corrections as well as additionalreferenced uses (please use the feedback mechanism to add uses).

the sulphate, as permanent white or blanc fixe, is used in paint, in X-ray diagnostic work (BaSO4)

glassmaking barite is extensively used as a weighting agent in oil well drilling fluids, and in

making rubber the carbonate is a rat poison the nitrate and chlorate give green colours (CARE!) in pyrotechnics sulphide is a white pigment making rubber rat poison

Barium: geological information

Elemental barium is never found in nature. Barium mainly is found in the ores barite and to a lesser extent in witherite.

Abundances of barium in various environments

In this table of abundances, values are given in units of ppb (parts per billion; 1 billion = 109), both in terms of weight and in terms of numbers of atoms. Values for abundances are difficult to determine with certainty, so all values should be treated with some caution, especially so for the less common elements. Local concentrations of any element can vary from those given here an orders of magnitude or so and values in various literature sources for less common elements do seem to vary considerably.

Abundances for barium in a number of different environments. Use the links in the location column for definitions, literature sources, and visual representations in many different styles (one of which is shown below)

Location ppb by weight ppb by atoms

Universe 10 0.09

Sun 10 0.1

Meteorite (carbonaceous) 2800 410

Crustal rocks 340000 51000

Sea water 30 1.4

Stream 25 0.2

Human 300 14

Log abundance (by atom numbers) in our sun

The chart above shows the log of the abundance (on a parts per billion scale) of the elements by atom number in our sun. Notice the "sawtooth" effect where elements with even atomic numbers tend to be more strongly represented than those with odd atomic numbers. This shows up best using the "Bar chart" option on the chart.

Barium: biological information

Biological roleof barium: barium has no biological role. The British Pharmaceutical Codex from 1907 indicates that barium chloride ["barii chloridum", BaCl2.2H2O] has a stimulant action on the heart and other muscles. It was said that it "raises blood pressure by constricting the vessels and tends to empty the intestines, bladder, and gall bladder". Its poisonous nature was also pointed out. Barium sulphide (BaS) was used as a depilatory agent (removes hair). Barium sulphate (BaSO4) is insoluble and used for body imaging (barium meal).

Levels in humansTable: the abundances of the elements in humans.

Human abundance by weight 300 ppb by weight

Human abundance by atoms 14 atoms relative to C = 1000000

How much barium is in your body? Find out here.

You can use this form to calculate how much barium your body contains. Enter your weight in either kilograms or pounds and click the "Calculate" button. You must enter a number, not text!Elements for which there are no data will always give a value of zero for the weight, no matter what you put in the weight box.

Calculate how much barium is in your body

Enter your weight here:

You contain about : grams of barium

Hazards and Risks

Hazards and risks associated with barium: barium compounds are encountered rarely by most people. All barium compounds should be regarded as highly toxic although initial evidence would appear to suggest the danger is limited. Barium salts may damage the liver. The metal dust presents a fire and explosion hazard.

Barium compounds

This section lists some binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and some other compounds of

0 0

barium. For each compound, a formal oxidation number for barium is given, but the usefulness of this number is limited for p-block elements in particular. Based upon that oxidation number, an electronic configuration is also given but note that for more exotic compounds you should view this as a guide only. The term hydride is used in a generic sense to indicate compounds of the type MxHy and not necessarily to indicate that any compounds listed behave chemically as hydrides. In compounds of barium (where known), the most common oxidation numbers of barium are: 2.

Hydrides

The term hydride is used to indicate compounds of the type MxHyand not necessarily to indicate that any compounds listed behave as hydrides chemically.

Barium dihydride : BaH2

Fluorides

Barium difluoride : BaF2

Chlorides

Barium dichloride : BaCl2

Barium dichloride dihydrate : BaCl2.2H2O

Bromides

Barium dibromide dihydrate : BaBr2.2H2O

Iodides

Barium diiodide : BaI2

Barium diiodide dihydrate : BaI2.2H2O

Oxides

Barium oxide : BaO Barium peroxide : BaO2

Sulfides

Barium sulphide : BaS Barium trisulphide : Ba(S3)

Selenides

Barium selenide : BaSe

Tellurides

none listed

Nitrides

Tribarium dinitride : Ba3N2

Carbonyls

none listed

Complexes

none listed

Standard Reduction Potentials

Barium: electronegativities

The most used definition of electronegativity is that an element's electronegativity is the power of an atom when in a molecule to attract electron density to itself. The electronegativity depends upon a number of factors and in particuler as the other atoms in the molecule. The first scale of electronegativity was developed by Linus Pauling and on his scale barium has a value of 0.89 on a scale running from from about 0.7 (an estimate for francium) to 2.20 (for hydrogen) to 3.98 (fluorine). Electronegativity has no units but "Pauling units" are often used when indicating

values mapped on to the Pauling scale. On the interactive plot below you may find the "Ball chart" and "Shaded table" styles most useful.

Table of Different types of electronegativity for barium. Use the links in the "Electronegativity" column for definitions, literature sources, and visual representations in many different styles (one of which is shown below). All values are quoted on the Pauling scale.

Electronegativity Value in Pauling units

Pauling electronegativity 0.89

Sanderson electronegativity 0.68

Allred Rochow electronegativity 0.97

Mulliken-Jaffe electronegativity 0.88 (sp orbital)

Allen electronegativity no data

Pauling electronegativities (all values are quoted on the Pauling scale.

There are a number of ways to produce a set of numbers representing electronegativity and five are given in the table above. The Pauling scale is perhaps the most famous and suffices for many purposes.

Barium: bond enthalpies in gaseous diatomic species

The bond energy in the gaseous diatomic species BaBa is (no data) kJ mol-1.

The following values refer to neutral heterodiatomic molecules in the gas phase. These numbers may well differ considerably from, say, single bond energies in a solid. All values are given in kJ mol-1.

Table of diatomic BaX bond enthalpies. All values are quoted in kJ mol-1.Each formula in the table (BaO, BaF, and so on) is a link - select these to see visual periodicity representations for bond enthalpies involving barium to elements of your choice.

Period 1BaH BaHe

176.0 ±14.6

Period 2BaLi BaBe BaB BaC BaN BaO BaF BaNe

561.9 ±13.4 587.0 ±6.7

Period 3BaNa BaMg BaAl BaSi BaP BaS BaCl BaAr

400.0 ±18.8 436.0 ±8.4

Period 4BaK BaCa BaGa BaGe BaAs BaSe BaBr BaKr

362.8 ±8.4

Period 5BaRb BaSr BaIn BaSn BaSb BaTe BaI BaXe

320.8 ±6.3

Period 6BaCs BaBa BaTl BaPb BaBi BaPo BaAt BaRn

Period 7BaFr BaRa

Notes

Barium: lattice energies

All values of lattice energiesare quoted in kJ mol-1.

Fluorides

BaF2:

thermochemical cycle: 2352 kJ mol-1

calculated: 2341 kJ mol-1

Chlorides

BaCl2:

thermochemical cycle: 2056 kJ mol-1

calculated: 2033 kJ mol-1

Bromides

BaBr2:

thermochemical cycle: 1985 kJ mol-1

calculated: 1950 kJ mol-1

Iodides

BaI2:

thermochemical cycle: 1877 kJ mol-1

calculated: 1831 kJ mol-1

Hydrides

BaH2:

thermochemical cycle: 2121 kJ mol-1

calculated: 2121 kJ mol-1

Oxides

BaO:

thermochemical cycle: 3054 kJ mol-1

calculated: 3029 kJ mol-1

Barium: physical properties

Temperatures

Melting point: 1000 [or 727 °C (1341 °F)] K

Boiling point: 2143 [or 1870 °C (3398 °F)] K

Liquid range: 1143  K

Critical temperature: no data  K

Superconduction temperature: no data  K

Animate the above image by quicktime movie Animate the above image by animated gif

Expansion and conduction properties

Thermal conductivity: 18  W m-1 K-1

Coefficient of linear thermal expansion: 20.6  x 10-6 K-1

Bulk properties

Density of solid: 3510  kg m-3

Molar volume: 38.16  cm3

Velocity of sound: 1620  m s-1

Elastic properties

Young's modulus: 13  GPa

Rigidity modulus: 4.9  GPa

Bulk modulus: 9.6  GPa

Poisson's ratio: no data  (no units)

Hardnesses

Mineral hardness: 1.25  (no units)

Brinell hardness: no data  MN m-2

Vickers hardness: no data  MN m-2

Electrical properties

Electrical resistivity: 34  10-8 Ω m; or mΩ cm

Optical properties

Reflectivity: no data  %

Refractive index: no data  (no units)

Chemical reactions of the elements

Reaction of barium with air

Barium is a silvery white metal. The surface of barium metal is covered with a thin layer of oxide that helps protect the metal from attack by air, but to a lesser extent than the corresponding layer in magnesium. Once ignited, barium metal burns in air to give a mixture of white barium oxide, BaO, and barium nitride, Ba3N2. Barium oxide is more normally made by heating barium carbonate. The superoxide BaO2 apparently is also formed in this reaction. Barium, three places below magnesium in the periodic table is more reactive with air than magnesium.

2Ba(s) + O2(g) → 2BaO(s)

Ba(s) + O2(g) → BaO2(s)

3Ba(s) + N2(g) → Ba3N2(s)

Reaction of barium with water

Barium reacts readily with water to form barium hydroxide, Ba(OH)2and hydrogen gas (H2). The reaction is quicker than that of strontium (immediately above barium in the periodic table) but probably slower than that of radium (immediately below barium in the periodic table).

Ba(s) + 2H2O(g) → Ba(OH)2(aq) + H2(g)

Reaction of barium with the halogens

I expect barium is very reactive towards the halogens, but I've not yet found explicit references to that effect. So, it is epxected that chlorine, Cl2 bromine, Br2, or iodine, I2, would burn to form the dihalides barium(II) chloride, BaCl2, barium(II) bromide, BaBr2, and barium(II) iodide, BaI2 respectively. The reactions with bromine and with iodine wolud probably require heat.

Ba(s) + Cl2(g) → BaCl2(s)

Ba(s) + Br2(g) → BaBr2(s)

Ba(s) + I2(g) → BaI2(s)

Reaction of barium with acids

Reaction of barium with bases

Barium: crystal structure

Space group: Im-3m (Space group number: 229) Structure: bcc (body-centred cubic) Cell parameters:

o a: 502.8 pmo b: 502.8 pmo c: 502.8 pmo α: 90.000°o β: 90.000°o γ: 90.000°

You may view the structure of barium:

interactively  (Jmol) or non-interactively

References

Barium: enthalpies and thermodynamic properties

Enthalpies

Enthalpy of fusion : 8.0  kJ mol-1

Enthalpy of vaporisation : 140  kJ mol-1

Enthalpy of atomisation : 182  kJ mol-1

Thermodynamic dataTable: thermodynamic data for barium.

State ΔfH° ΔfG° S° CpH H°298.15-H°0

Units kJ mol-1 kJ mol-1 J K-1 mol-1 J K-1 mol-1 kJ mol-1

Solid 0 0 63 28.1 6.9

Gas 181 146 170.13 20.79 6.20

Notes

This tables gives a few thermodynamic data. Most values are those given in the NBS technical notes (reference 1) after conversion from the units used within those notes. Values labelled with an asterisk (*) are Committee on Data for Science and Technology (CODATA) agreed values for the thermodynamic properties of key chemical substances (reference 2). These values are published in a number of places including the WWW (reference 3).

Properties of barium atoms

Ionisation Energies and electron affinity

The electron affinity of barium is 13.95  kJ mol-1. The ionisation energies of barium are given below.

Ionisation energy number Enthalpy /kJ mol-1

1st 502.9

2nd 965.2

3rd 3600

Electronic configuration

The following represents the electronic configuration and its associated term symbol for the ground state neutral gaseous atom. The configuration associated with barium in its compounds is not necessarily the same.

Ground state electron configuration :  [Xe].6s2

Shell structure :  2.8.18.18.8.2 Term symbol :   1S0

A schematic representation of the shell structure of barium - not what the atom of barium "looks like".

Size of barium in several environments

One measure of size is the element-element distance within the element. It is not always easy to make sensible comparisons between the elements however as some bonds are quite short because of multiple bonding (for instance the O=O distance in O2 is short because of the the double bond connecting the two atoms. The bond length in BaBa is: 434.7 pm.

There are several other ways ways to define radius for atoms and ions. Follow the appropriate hyperlinks for literature references and definitions of each type of radius. All values of radii are given in picometres (pm). Conversion factors are:

1 pm = 1 x 10-12 metre (meter) 100 pm = 1 Ångstrom 1000 pm = 1 nanometre (nm, nanometer)

Neutral radii

The size of neutral atoms depends upon the way in which the measurement is made and the environment. Follow the appropriate hyperlinks for definitions of each radius type. The term "atomic radius" is not particularly helpful although its use is widespread. The problem is its meaning, which is clearly very different in different

sources and books. Two values are given here, one is based upon calculations and the other upon observation - follow the appropriate link for further details.

Atomic radius (empirical): 215  pm

Atomic radius (calculated): 253  pm

Covalent radius (2008 values): 215  pm

Molecular single bond covalent radii: 196 (coordination number 2) pm

Molecular double bond covalent radii: 161  pm

Molecular triple bond covalent radii: 149  pm

Covalent radius (empirical): 198  pm

van der Waals radius: no information  pm

Ionic radii

This table gives some ionic radii. In this table, geometry refers to the arrangment of the ion's nearest neighbours. Size does depend upon geometry and environment. For electronic configurations, where it matters, the values given for octahedral species are low spin unless stated to be high spin. The terms low spin and high spin refer to the electronic configurations of particular geomtries of certain d-block metal ions. Further information is available in inorganic chemistry textbooks, usually at Level 1 or First Year University level. For definitions of ionic radius and further information, follow the hypertext link.

Ion Coordination type Radius / pm

Ba(II) 6-coordinate, octahedral 149

Ba(II) 8-coordinate

156

Pauling ionic radiiThis table shows Pauling radii for barium

Ion Pauling radius / pm

Ba(I)153

Ba(II)135

Isotopes of barium

Barium isotopes are used a wide variety of fields and applications. Ba-130 is used in the production of Ba-131/Cs-131 which is used in brachytherapy (seeds). Ba-132 can be used for the production of Ba-133 which is used as a gamma reference source. Ba-134 has been used to perform experiments in the field of nuclear physics. Ba-136 has been used to study photon scattering phenomena. Both Ba-136 and Ba-138 have been used in activation cross section experiments. Ba-135 has been used to validate the use of spinor symmetry while Ba-137 has been used in periments regarding the theory of relativistic coupled clusters. Finally, Ba-138 has been used in studying so-called r- and s-processes in stars. Barium isotopes can be obtained from Trace Sciences International.

< class="s">Naturally occurring isotopes r align="center">This table shows information about naturally occuring isotopes, their atomic masses, their natural abundances, their nuclear spins, and their magnetic moments. Further data for radioisotopes (radioactive isotopesof barium are listed (including any which occur naturally) below.

Isotope Atomic mass (ma/u)

Natural abundance (atom %)

Nuclear spin (I)

Magnetic moment (μ/μN)

130Ba 129.906282 (8) 0.106 (1) 0132Ba 131.905042 (9) 0.101 (1) 0134Ba 133.904486 (7) 2.417 (18) 0135Ba 134.905665 (7) 6.592 (12) 3sub>2 0.837943136Ba 135.904553 (7) 7.854 (24) 0137Ba 136.905812

(6)td>11.232 (24) 3/2 0.937365

138Ba 137.905232 (6) 71.698 (42) 0

In the above picture, the most intense ion is set to 100% since this corresponds best to the output from a mass spectrometer. This is not to be confused with the relative percentage isope abundances which total 100% for all the naturally occurring isotopes.

Radiosotope datad>128.90868<="" td="">

Further data for naturally occuring isotopes of barium are listed above. This table gives iormation about some radiosotopes of barium, their masses, their half-lives, their modes of decay, their nuclear spins, and their nuclear magnetic moments.

Isotope Mass Half-life de of decay Nuclear spin Nuclear magnetic moment

128Ba 127.90831 2.43 d EC to128Cs 0

129Ba 2.2 h EC to129Cs 1/2 -0.40

131Ba 130.90693 11.7 d EC to131Cs 1/20.7081

133Ba 132.906003 10.53 y EC to133Cs 1/2 0.7717

139Ba 138.908836 β- to139La 7/2 -0.97

140Ba 139.91060 12.75 d β- to140La 0

NMR Properties of barium

Common reference compound: BaCl2/D2O.

Table of NMR-active nucleus propeties of barium

Isotope 1 Isotope 2 Isotope 3

Isotope 135Ba 137Ba

Natural abundance /% 6.592 11.23

Spin (I) 3/23/2

Frequency relative to 1H = 100 (MHz) 9.934414 11.112889

Receptivity, DP, relative to 1H = 1.00 0.00330 0.00786

Receptivity, DC, relative to 13C = 1.00 1.88 4.49

Magnetogyric ratio, γ (107 rad T-1 s-1) 2.65750 2.99295

Magnetic moment, μ (μN) 1.08178 1.21013

Nuclear quadrupole moment, Q/millibarn +160(3) +245(4)

Line width factor, 1056l (m4) 0.034 0.080

References

Barium: orbital properties

Valence shell orbital radii

The following are calculated values of valence shell orbital radii, Rmax

Table: valence shell orbital radii for barium.

Orbital Radius [/pm] Radius [/AU]

s orbital 235.4 4.44826

p orbital no data no data

d orbital no data no data

f orbital no data no data