Element: Barium
General data
| Element name | Barium |
|---|---|
| Chemical symbol | Ba |
| Atomic number Z | 56 |
| Year discovered | 1808 |
| Standard state (25°C) | Solid |
| Category | Alkaline earth metal |
| Block | s |
| Atomic mass | 137.33 |
| CPK color | #00C900 |
Physical properties
| Melting point | 1000 K (727 °C) |
|---|---|
| Boiling point | 2170 K (1897 °C) |
| Density | 3.62 g/cm³ |
Energy properties
| First ionization energy | 5.212 eV |
|---|---|
| Electron affinity | no data |
Atomic structure
| Protons | 56 (Atomic number) |
|---|---|
| Neutrons (Ba-138, most abundant isotope) | 82 |
| Electrons | 56 |
| Electron configuration | [Xe] 6s² |
| Oxidation states | +2 |
| Electronegativity (Pauling) | 0.89 |
| Atomic radius (van der Waals) | 268 pm |
Ionization energies - NIST ASD (56 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Ba I | 0+ | 5.2116646 ± 0.0000012 | measured |
| Ba II | 1+ | 10.003826 ± 0.000012 | measured |
| Ba III | 2+ | 35.8438 ± 0.0025 | measured |
| Ba IV | 3+ | 47 ± 0.3 | semi-empirical |
| Ba V | 4+ | 58 ± 1.9 | calculated |
| Ba VI | 5+ | 71 ± 2 | calculated |
| Ba VII | 6+ | 86 ± 2 | calculated |
| Ba VIII | 7+ | 101 ± 2.1 | calculated |
| Ba IX | 8+ | 130.5 ± 0.6 | semi-empirical |
| Ba X | 9+ | 146.52 ± 0.12 | semi-empirical |
| Ba XI | 10+ | 241 ± 2.4 | calculated |
| Ba XII | 11+ | 267.1 ± 2.5 | calculated |
| Ba XIII | 12+ | 296 ± 3 | calculated |
| Ba XIV | 13+ | 325 ± 3 | calculated |
| Ba XV | 14+ | 354 ± 3 | calculated |
| Ba XVI | 15+ | 390 ± 3 | calculated |
| Ba XVII | 16+ | 422 ± 3 | calculated |
| Ba XVIII | 17+ | 455 ± 3 | calculated |
| Ba XIX | 18+ | 488 ± 3 | calculated |
| Ba XX | 19+ | 520 ± 4 | calculated |
| Ba XXI | 20+ | 646 ± 4 | calculated |
| Ba XXII | 21+ | 679 ± 4 | calculated |
| Ba XXIII | 22+ | 717 ± 4 | calculated |
| Ba XXIV | 23+ | 752 ± 4 | calculated |
| Ba XXV | 24+ | 809 ± 4 | calculated |
| Ba XXVI | 25+ | 846 ± 4 | calculated |
| Ba XXVII | 26+ | 935 ± 4 | calculated |
| Ba XXVIII | 27+ | 976.62 ± 0.11 | semi-empirical |
| Ba XXIX | 28+ | 1695 ± 4 | calculated |
| Ba XXX | 29+ | 1776 ± 4 | calculated |
| Ba XXXI | 30+ | 1864 ± 4 | calculated |
| Ba XXXII | 31+ | 1958 ± 4 | calculated |
| Ba XXXIII | 32+ | 2047 ± 4 | calculated |
| Ba XXXIV | 33+ | 2142 ± 5 | calculated |
| Ba XXXV | 34+ | 2256 ± 5 | calculated |
| Ba XXXVI | 35+ | 2349 ± 5 | calculated |
| Ba XXXVII | 36+ | 2452 ± 5 | calculated |
| Ba XXXVIII | 37+ | 2547 ± 4 | calculated |
| Ba XXXIX | 38+ | 2814 ± 4 | calculated |
| Ba XL | 39+ | 2901 ± 4 | calculated |
| Ba XLI | 40+ | 2994 ± 4 | calculated |
| Ba XLII | 41+ | 3081 ± 4 | calculated |
| Ba XLIII | 42+ | 3266 ± 4 | calculated |
| Ba XLIV | 43+ | 3363 ± 4 | calculated |
| Ba XLV | 44+ | 3546 ± 4 | calculated |
| Ba XLVI | 45+ | 3640 ± 4 | calculated |
| Ba XLVII | 46+ | 8326 ± 4 | calculated |
| Ba XLVIII | 47+ | 8565 ± 4 | calculated |
| Ba XLIX | 48+ | 8831 ± 4 | calculated |
| Ba L | 49+ | 9077 ± 4 | calculated |
| Ba LI | 50+ | 9739 ± 4 | calculated |
| Ba LII | 51+ | 10023 ± 4 | calculated |
| Ba LIII | 52+ | 10376 ± 4 | calculated |
| Ba LIV | 53+ | 10616.42 ± 0.05 | calculated |
| Ba LV | 54+ | 43485.37 ± 0.04 | calculated |
| Ba LVI | 55+ | 44561.633 ± 0.024 | calculated |
Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.
Photos
Isotopes (41)
| A | N | Half-life | Decay |
|---|---|---|---|
| Ba-114 | 58 | 0.41 s | EC/β⁺ |
| Ba-115 | 59 | 0.45 s | EC/β⁺ |
| Ba-116 | 60 | 1.3 s | EC/β⁺ |
| Ba-117 | 61 | 1.75 s | EC/β⁺ |
| Ba-118 | 62 | 5.2 s | EC/β⁺ |
| Ba-119 | 63 | 5.4 s | EC/β⁺ |
| Ba-120 | 64 | 24 s | EC/β⁺ |
| Ba-121 | 65 | 29.7 s | EC/β⁺ |
| Ba-122 | 66 | 1.95 min | EC/β⁺ |
| Ba-123 | 67 | 2.4 min | EC/β⁺ |
| Ba-124 | 68 | 10.8 min | EC/β⁺ |
| Ba-125 | 69 | 3.3 min | EC/β⁺ |
| Ba-126 | 70 | 98.6 min | EC/β⁺ |
| Ba-127 | 71 | 12.8 min | EC/β⁺ |
| Ba-128 | 72 | 2.43 d | EC |
| Ba-129 | 73 | 2.23 h | EC/β⁺ |
| Ba-130 | 74 | stable | - |
| Ba-131 | 75 | 11.52 d | EC/β⁺ |
| Ba-132 | 76 | stable | - |
| Ba-133 | 77 | 10.536 a | EC |
| Ba-134 | 78 | stable | - |
| Ba-135 | 79 | stable | - |
| Ba-136 | 80 | stable | - |
| Ba-137 | 81 | stable | - |
| Ba-138 | 82 | stable | - |
| Ba-139 | 83 | 82.89 min | β⁻ |
| Ba-140 | 84 | 12.7526 d | β⁻ |
| Ba-141 | 85 | 18.24 min | β⁻ |
| Ba-142 | 86 | 10.51 min | β⁻ |
| Ba-143 | 87 | 14.38 s | β⁻ |
| Ba-144 | 88 | 11.7 s | β⁻ |
| Ba-145 | 89 | 3.99 s | β⁻ |
| Ba-146 | 90 | 2.16 s | β⁻ |
| Ba-147 | 91 | 894 ms | β⁻ |
| Ba-148 | 92 | 619 ms | β⁻ |
| Ba-149 | 93 | 352 ms | β⁻ |
| Ba-150 | 94 | 258 ms | β⁻ |
| Ba-151 | 95 | 167 ms | β⁻ |
| Ba-152 | 96 | 140 ms | β⁻ |
| Ba-153 | 97 | 110 ms | β⁻ |
| Ba-154 | 98 | 50 ms | β⁻ |
Data sources
- PubChem Periodic Table API - Retrieved on 29 June 2026 - licence: CC0
- IUPAC CIAAW - Abridged Standard Atomic Weights 2024 - Table version: 2024 - licence: Public domain
- NNDC Wallet Cards 2023 - Data as of 15 October 2024 - licence: Public domain
- NIST Atomic Spectra Database (ASD) - Retrieved on 29 June 2026 - licence: © U.S. Secretary of Commerce
- Images of Elements - Retrieved on 29 June 2026 - licence: CC BY 3.0