Element: Strontium
General data
| Element name | Strontium |
|---|---|
| Chemical symbol | Sr |
| Atomic number Z | 38 |
| Year discovered | 1790 |
| Standard state (25°C) | Solid |
| Category | Alkaline earth metal |
| Block | s |
| Atomic mass | 87.62 |
| CPK color | #00FF00 |
Physical properties
| Melting point | 1050 K (777 °C) |
|---|---|
| Boiling point | 1655 K (1382 °C) |
| Density | 2.64 g/cm³ |
Energy properties
| First ionization energy | 5.695 eV |
|---|---|
| Electron affinity | no data |
Atomic structure
| Protons | 38 (Atomic number) |
|---|---|
| Neutrons (Sr-88, most abundant isotope) | 50 |
| Electrons | 38 |
| Electron configuration | [Kr] 5s² |
| Oxidation states | +2 |
| Electronegativity (Pauling) | 0.95 |
| Atomic radius (van der Waals) | 249 pm |
Ionization energies - NIST ASD (38 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Sr I | 0+ | 5.69486745 ± 0.00000012 | measured |
| Sr II | 1+ | 11.0302765 ± 0.0000025 | measured |
| Sr III | 2+ | 42.88353 ± 0.00019 | measured |
| Sr IV | 3+ | 56.28 ± 0.003 | semi-empirical |
| Sr V | 4+ | 70.7 ± 0.6 | semi-empirical |
| Sr VI | 5+ | 88 ± 2 | calculated |
| Sr VII | 6+ | 104 ± 2 | calculated |
| Sr VIII | 7+ | 121.21 ± 0.06 | semi-empirical |
| Sr IX | 8+ | 158.33 ± 0.25 | semi-empirical |
| Sr X | 9+ | 177.3 ± 0.06 | measured |
| Sr XI | 10+ | 324.07 ± 0.15 | measured |
| Sr XII | 11+ | 362 ± 2.5 | calculated |
| Sr XIII | 12+ | 408 ± 3 | calculated |
| Sr XIV | 13+ | 454 ± 3 | calculated |
| Sr XV | 14+ | 499 ± 3 | calculated |
| Sr XVI | 15+ | 562 ± 3 | calculated |
| Sr XVII | 16+ | 612 ± 3 | calculated |
| Sr XVIII | 17+ | 665 ± 3 | calculated |
| Sr XIX | 18+ | 722 ± 3 | calculated |
| Sr XX | 19+ | 774 ± 4 | calculated |
| Sr XXI | 20+ | 932 ± 3 | semi-empirical |
| Sr XXII | 21+ | 982.1 ± 1.1 | semi-empirical |
| Sr XXIII | 22+ | 1038 ± 1.5 | semi-empirical |
| Sr XXIV | 23+ | 1105 ± 4 | semi-empirical |
| Sr XXV | 24+ | 1165 ± 3 | semi-empirical |
| Sr XXVI | 25+ | 1211 ± 6 | semi-empirical |
| Sr XXVII | 26+ | 1333.4 ± 1.9 | semi-empirical |
| Sr XXVIII | 27+ | 1387.19 ± 0.05 | semi-empirical |
| Sr XXIX | 28+ | 3344.7 ± 1.9 | semi-empirical |
| Sr XXX | 29+ | 3497 ± 6 | semi-empirical |
| Sr XXXI | 30+ | 3664 ± 8 | semi-empirical |
| Sr XXXII | 31+ | 3830 ± 30 | semi-empirical |
| Sr XXXIII | 32+ | 4053 ± 4 | semi-empirical |
| Sr XXXIV | 33+ | 4232 ± 3 | semi-empirical |
| Sr XXXV | 34+ | 4465 ± 4 | semi-empirical |
| Sr XXXVI | 35+ | 4612.397 ± 0.011 | calculated |
| Sr XXXVII | 36+ | 19345.59 ± 0.005 | calculated |
| Sr XXXVIII | 37+ | 20025.2673 ± 0.0024 | 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 (36)
| A | N | Half-life | Decay |
|---|---|---|---|
| Sr-73 | 35 | 23.3 ms | EC/β⁺ |
| Sr-74 | 36 | 28 ms | EC/β⁺ |
| Sr-75 | 37 | 85.2 ms | EC/β⁺ |
| Sr-76 | 38 | 7.89 s | EC/β⁺ |
| Sr-77 | 39 | 9.0 s | EC/β⁺ |
| Sr-78 | 40 | 156 s | EC/β⁺ |
| Sr-79 | 41 | 2.23 min | EC/β⁺ |
| Sr-80 | 42 | 106.3 min | EC/β⁺ |
| Sr-81 | 43 | 22.3 min | EC/β⁺ |
| Sr-82 | 44 | 25.35 d | EC |
| Sr-83 | 45 | 32.41 h | EC/β⁺ |
| Sr-84 | 46 | stable | - |
| Sr-85 | 47 | 64.849 d | EC |
| Sr-86 | 48 | stable | - |
| Sr-87 | 49 | stable | - |
| Sr-88 | 50 | stable | - |
| Sr-89 | 51 | 50.56 d | β⁻ |
| Sr-90 | 52 | 28.905 a | β⁻ |
| Sr-91 | 53 | 9.68 h | β⁻ |
| Sr-92 | 54 | 2.610 h | β⁻ |
| Sr-93 | 55 | 7.43 min | β⁻ |
| Sr-94 | 56 | 75.3 s | β⁻ |
| Sr-95 | 57 | 23.90 s | β⁻ |
| Sr-96 | 58 | 1.065 s | β⁻ |
| Sr-97 | 59 | 431 ms | β⁻ |
| Sr-98 | 60 | 653 ms | β⁻ |
| Sr-99 | 61 | 269 ms | β⁻ |
| Sr-100 | 62 | 201 ms | β⁻ |
| Sr-101 | 63 | 114 ms | β⁻ |
| Sr-102 | 64 | 72 ms | β⁻ |
| Sr-103 | 65 | 56 ms | β⁻ |
| Sr-104 | 66 | 51 ms | β⁻ |
| Sr-105 | 67 | 39 ms | β⁻ |
| Sr-106 | 68 | 20 ms | β⁻ |
| Sr-107 | 69 | unknown | β⁻ |
| Sr-108 | 70 | unknown | 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