Element: Rhodium
General data
| Element name | Rhodium |
|---|---|
| Chemical symbol | Rh |
| Atomic number Z | 45 |
| Year discovered | 1803 |
| Standard state (25°C) | Solid |
| Category | Transition metal |
| Block | d |
| Atomic mass | 102.91 |
| CPK color | #0A7D8C |
Physical properties
| Melting point | 2237 K (1964 °C) |
|---|---|
| Boiling point | 3968 K (3695 °C) |
| Density | 12.4 g/cm³ |
Energy properties
| First ionization energy | 7.459 eV |
|---|---|
| Electron affinity | 1.137 eV |
Atomic structure
| Protons | 45 (Atomic number) |
|---|---|
| Neutrons (Rh-103, most abundant isotope) | 58 |
| Electrons | 45 |
| Electron configuration | [Kr] 5s¹ 4d⁸ |
| Oxidation states | +3 |
| Electronegativity (Pauling) | 2.28 |
| Atomic radius (van der Waals) | 195 pm |
Ionization energies - NIST ASD (45 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Rh I | 0+ | 7.4589 ± 0.00005 | measured |
| Rh II | 1+ | 18.08 | semi-empirical |
| Rh III | 2+ | 31.06 | semi-empirical |
| Rh IV | 3+ | 42 ± 1.7 | calculated |
| Rh V | 4+ | 63 ± 1.9 | calculated |
| Rh VI | 5+ | 80 ± 2 | calculated |
| Rh VII | 6+ | 97 ± 2 | calculated |
| Rh VIII | 7+ | 115.1 ± 2.1 | calculated |
| Rh IX | 8+ | 135 ± 2.2 | calculated |
| Rh X | 9+ | 207.51 ± 0.05 | semi-empirical |
| Rh XI | 10+ | 228 ± 2.4 | calculated |
| Rh XII | 11+ | 252.1 ± 2.5 | calculated |
| Rh XIII | 12+ | 277 ± 3 | calculated |
| Rh XIV | 13+ | 306 ± 3 | calculated |
| Rh XV | 14+ | 331.58 ± 0.14 | semi-empirical |
| Rh XVI | 15+ | 389.3 ± 0.5 | calculated |
| Rh XVII | 16+ | 415.97 ± 0.14 | semi-empirical |
| Rh XVIII | 17+ | 739 ± 3 | calculated |
| Rh XIX | 18+ | 794 ± 3 | calculated |
| Rh XX | 19+ | 857 ± 4 | calculated |
| Rh XXI | 20+ | 921 ± 4 | calculated |
| Rh XXII | 21+ | 984 ± 4 | calculated |
| Rh XXIII | 22+ | 1061 ± 4 | calculated |
| Rh XXIV | 23+ | 1131 ± 4 | calculated |
| Rh XXV | 24+ | 1202 ± 4 | calculated |
| Rh XXVI | 25+ | 1274 ± 4 | calculated |
| Rh XXVII | 26+ | 1344 ± 4 | calculated |
| Rh XXVIII | 27+ | 1544 ± 5 | semi-empirical |
| Rh XXIX | 28+ | 1604.9 ± 1.7 | semi-empirical |
| Rh XXX | 29+ | 1677.6 ± 2.2 | semi-empirical |
| Rh XXXI | 30+ | 1763 ± 7 | semi-empirical |
| Rh XXXII | 31+ | 1851 ± 4 | semi-empirical |
| Rh XXXIII | 32+ | 1903 ± 9 | semi-empirical |
| Rh XXXIV | 33+ | 2063 ± 3 | semi-empirical |
| Rh XXXV | 34+ | 2129.22 ± 0.07 | semi-empirical |
| Rh XXXVI | 35+ | 5018 ± 3 | semi-empirical |
| Rh XXXVII | 36+ | 5203 ± 8 | semi-empirical |
| Rh XXXVIII | 37+ | 5406 ± 11 | semi-empirical |
| Rh XXXIX | 38+ | 5600 ± 40 | semi-empirical |
| Rh XL | 39+ | 5940 ± 7 | semi-empirical |
| Rh XLI | 40+ | 6161 ± 5 | semi-empirical |
| Rh XLII | 41+ | 6444 ± 6 | semi-empirical |
| Rh XLIII | 42+ | 6623.262 ± 0.02 | calculated |
| Rh XLIV | 43+ | 27486.979 ± 0.012 | calculated |
| Rh XLV | 44+ | 28312.031 ± 0.006 | 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 (40)
| A | N | Half-life | Decay |
|---|---|---|---|
| Rh-89 | 44 | < 120 ns | EC/β⁺ |
| Rh-90 | 45 | 29 ms | EC/β⁺ |
| Rh-91 | 46 | 1.47 s | EC/β⁺ |
| Rh-92 | 47 | 5.64 s | EC/β⁺ |
| Rh-93 | 48 | 12.2 s | EC/β⁺ |
| Rh-94 | 49 | 70.6 s | EC/β⁺ |
| Rh-95 | 50 | 5.02 min | EC/β⁺ |
| Rh-96 | 51 | 9.57 min | EC/β⁺ |
| Rh-97 | 52 | 30.8 min | EC/β⁺ |
| Rh-98 | 53 | 8.74 min | EC/β⁺ |
| Rh-99 | 54 | 16.1 d | EC/β⁺ |
| Rh-100 | 55 | 20.5 h | EC/β⁺ |
| Rh-101 | 56 | 4.07 a | EC |
| Rh-102 | 57 | 207.3 d | EC/β⁺ |
| Rh-103 | 58 | stable | - |
| Rh-104 | 59 | 42.3 s | β⁻ |
| Rh-105 | 60 | 35.341 h | β⁻ |
| Rh-106 | 61 | 30.1 s | β⁻ |
| Rh-107 | 62 | 21.7 min | β⁻ |
| Rh-108 | 63 | 17.0 s | β⁻ |
| Rh-109 | 64 | 80.8 s | β⁻ |
| Rh-110 | 65 | 3.3 s | β⁻ |
| Rh-111 | 66 | 11 s | β⁻ |
| Rh-112 | 67 | 3.5 s | β⁻ |
| Rh-113 | 68 | 2.80 s | β⁻ |
| Rh-114 | 69 | 1.82 s | β⁻ |
| Rh-115 | 70 | 0.99 s | β⁻ |
| Rh-116 | 71 | 690 ms | β⁻ |
| Rh-117 | 72 | 420 ms | β⁻ |
| Rh-118 | 73 | 286 ms | β⁻ |
| Rh-119 | 74 | 189 ms | β⁻ |
| Rh-120 | 75 | 133 ms | β⁻ |
| Rh-121 | 76 | 73 ms | β⁻ |
| Rh-122 | 77 | 52.3 ms | β⁻ |
| Rh-123 | 78 | 42.2 ms | β⁻ |
| Rh-124 | 79 | 32 ms | β⁻ |
| Rh-125 | 80 | 26.5 ms | β⁻ |
| Rh-126 | 81 | 19 ms | β⁻ |
| Rh-127 | 82 | 20 ms | β⁻ |
| Rh-128 | 83 | 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