Element: Mendelevium
This element has only been produced a few atoms at a time, so most of its properties have never been measured - missing values are omitted.
General data
| Element name | Mendelevium |
|---|---|
| Chemical symbol | Md |
| Atomic number Z | 101 |
| Year discovered | 1955 |
| Standard state (25°C) | Solid |
| Category | Actinide |
| Block | f |
| Atomic mass | [258] |
| CPK color | #B30DA6 |
Physical properties
| Melting point | 1100 K (827 °C) |
|---|
Energy properties
| First ionization energy | 6.58 eV |
|---|
Atomic structure
| Protons | 101 (Atomic number) |
|---|---|
| Neutrons (Md-258, longest-lived isotope) | 157 |
| Electrons | 101 |
| Electron configuration | [Rn] 7s² 5f¹³ |
| Oxidation states | +3, +2 |
| Electronegativity (Pauling) | 1.3 |
Ionization energies - NIST ASD (101 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Md I | 0+ | 6.58 ± 0.07 | semi-empirical |
| Md II | 1+ | 12.4 ± 0.4 | semi-empirical |
| Md III | 2+ | 24.3 ± 0.4 | semi-empirical |
| Md IV | 3+ | 40 ± 0.4 | semi-empirical |
| Md V | 4+ | 54.1 ± 1.9 | calculated |
| Md VI | 5+ | 76 ± 2 | calculated |
| Md VII | 6+ | 96 ± 2 | calculated |
| Md VIII | 7+ | 115.1 ± 2.1 | calculated |
| Md IX | 8+ | 143.9 ± 2.2 | calculated |
| Md X | 9+ | 162 ± 2.2 | calculated |
| Md XI | 10+ | 187 ± 2.4 | calculated |
| Md XII | 11+ | 215 ± 11 | calculated |
| Md XIII | 12+ | 240 ± 12 | calculated |
| Md XIV | 13+ | 260 ± 12 | calculated |
| Md XV | 14+ | 282 ± 14 | calculated |
| Md XVI | 15+ | 307 ± 15 | calculated |
| Md XVII | 16+ | 334 ± 16 | calculated |
| Md XVIII | 17+ | 360 ± 17 | calculated |
| Md XIX | 18+ | 386 ± 20 | calculated |
| Md XX | 19+ | 412 ± 21 | calculated |
| Md XXI | 20+ | 438 ± 22 | calculated |
| Md XXII | 21+ | 462 ± 4 | calculated |
| Md XXIII | 22+ | 486 ± 4 | calculated |
| Md XXIV | 23+ | 659 ± 4 | calculated |
| Md XXV | 24+ | 690 ± 4 | calculated |
| Md XXVI | 25+ | 723 ± 4 | calculated |
| Md XXVII | 26+ | 760 ± 4 | calculated |
| Md XXVIII | 27+ | 794 ± 4 | calculated |
| Md XXIX | 28+ | 828 ± 4 | calculated |
| Md XXX | 29+ | 885 ± 4 | calculated |
| Md XXXI | 30+ | 920 ± 4 | calculated |
| Md XXXII | 31+ | 958 ± 4 | calculated |
| Md XXXIII | 32+ | 994 ± 4 | calculated |
| Md XXXIV | 33+ | 1160 ± 60 | calculated |
| Md XXXV | 34+ | 1210 ± 60 | calculated |
| Md XXXVI | 35+ | 1250 ± 60 | calculated |
| Md XXXVII | 36+ | 1290 ± 60 | calculated |
| Md XXXVIII | 37+ | 1430 ± 70 | calculated |
| Md XXXIX | 38+ | 1480 ± 70 | calculated |
| Md XL | 39+ | 1620 ± 80 | calculated |
| Md XLI | 40+ | 1660 ± 80 | calculated |
| Md XLII | 41+ | 1840 ± 90 | calculated |
| Md XLIII | 42+ | 1930 ± 100 | calculated |
| Md XLIV | 43+ | 2020 ± 100 | calculated |
| Md XLV | 44+ | 2110 ± 110 | calculated |
| Md XLVI | 45+ | 2200 ± 110 | calculated |
| Md XLVII | 46+ | 2290 ± 120 | calculated |
| Md XLVIII | 47+ | 2390 ± 120 | calculated |
| Md XLIX | 48+ | 2480 ± 120 | calculated |
| Md L | 49+ | 2580 ± 120 | calculated |
| Md LI | 50+ | 2680 ± 140 | calculated |
| Md LII | 51+ | 2760 ± 140 | calculated |
| Md LIII | 52+ | 2860 ± 150 | calculated |
| Md LIV | 53+ | 2950 ± 150 | calculated |
| Md LV | 54+ | 3050 ± 150 | calculated |
| Md LVI | 55+ | 3513 ± 5 | calculated |
| Md LVII | 56+ | 3592 ± 5 | calculated |
| Md LVIII | 57+ | 3675 ± 6 | calculated |
| Md LIX | 58+ | 3762 ± 6 | calculated |
| Md LX | 59+ | 3845 ± 7 | calculated |
| Md LXI | 60+ | 3926 ± 10 | calculated |
| Md LXII | 61+ | 4109 ± 12 | calculated |
| Md LXIII | 62+ | 4194 ± 15 | calculated |
| Md LXIV | 63+ | 4286 ± 19 | calculated |
| Md LXV | 64+ | 4371 ± 24 | calculated |
| Md LXVI | 65+ | 4720 ± 30 | calculated |
| Md LXVII | 66+ | 4800 ± 40 | calculated |
| Md LXVIII | 67+ | 4890 ± 40 | calculated |
| Md LXIX | 68+ | 4970 ± 50 | calculated |
| Md LXX | 69+ | 5580 ± 50 | calculated |
| Md LXXI | 70+ | 5680 ± 60 | calculated |
| Md LXXII | 71+ | 5930 ± 60 | calculated |
| Md LXXIII | 72+ | 6030 ± 70 | calculated |
| Md LXXIV | 73+ | 9430 ± 90 | calculated |
| Md LXXV | 74+ | 9620 ± 90 | calculated |
| Md LXXVI | 75+ | 9810 ± 100 | calculated |
| Md LXXVII | 76+ | 10020 ± 110 | calculated |
| Md LXXVIII | 77+ | 10220 ± 120 | calculated |
| Md LXXIX | 78+ | 10410 ± 120 | calculated |
| Md LXXX | 79+ | 10930 ± 140 | calculated |
| Md LXXXI | 80+ | 11130 ± 150 | calculated |
| Md LXXXII | 81+ | 11350 ± 160 | calculated |
| Md LXXXIII | 82+ | 11560 ± 170 | calculated |
| Md LXXXIV | 83+ | 12130 ± 190 | calculated |
| Md LXXXV | 84+ | 12310 ± 200 | calculated |
| Md LXXXVI | 85+ | 12500 ± 220 | calculated |
| Md LXXXVII | 86+ | 12680 ± 240 | calculated |
| Md LXXXVIII | 87+ | 14560 ± 250 | calculated |
| Md LXXXIX | 88+ | 14800 ± 300 | calculated |
| Md XC | 89+ | 15200 ± 300 | calculated |
| Md XCI | 90+ | 15400 ± 300 | calculated |
| Md XCII | 91+ | 31000 ± 300 | calculated |
| Md XCIII | 92+ | 31500 ± 400 | calculated |
| Md XCIV | 93+ | 32000 ± 400 | calculated |
| Md XCV | 94+ | 32500 ± 400 | calculated |
| Md XCVI | 95+ | 39500 ± 400 | calculated |
| Md XCVII | 96+ | 40100 ± 400 | calculated |
| Md XCVIII | 97+ | 41000 ± 400 | calculated |
| Md XCIX | 98+ | 41548 ± 6 | calculated |
| Md C | 99+ | 162066 ± 7 | calculated |
| Md CI | 100+ | 164764 ± 7 | 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 (17)
| A | N | Half-life | Decay |
|---|---|---|---|
| Md-244 | 143 | 0.39 s | α |
| Md-245 | 144 | 0.33 s | α |
| Md-246 | 145 | 0.9 s | α |
| Md-247 | 146 | 1.20 s | α |
| Md-248 | 147 | 7 s | EC/β⁺ |
| Md-249 | 148 | 25.6 s | α |
| Md-250 | 149 | 53 s | EC/β⁺ |
| Md-251 | 150 | 4.27 min | EC/β⁺ |
| Md-252 | 151 | 2.3 min | EC/β⁺ |
| Md-253 | 152 | 6 min | EC/β⁺ |
| Md-254 | 153 | 10 min | EC/β⁺ |
| Md-255 | 154 | 27 min | EC |
| Md-256 | 155 | 77.7 min | EC/β⁺ |
| Md-257 | 156 | 5.52 h | EC |
| Md-258 | 157 | 51.5 d | α |
| Md-259 | 158 | 1.61 h | SF |
| Md-260 | 159 | 31.8 d | α |
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