Periodic Table/Mendelevium
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101Md258 Da

Mendelevium

Actinide·Period 7·f-block

Radioactive metallic transuranic element. Belongs to the actinoid series. Only known isotope, Md-256 has a half-life of 1.3 hours. First identified by Glenn T. Seaborg, Albert Ghiorso and associates in 1955. Alternative name Unnilunium has been proposed. Named after the 'inventor' of the periodic table, Dmitri Mendeleev.

Gallery

This is only an illustration, not mendelevium itself. Chemically similar to Thulium, the highly radioactive heavy metal emits very energetic α-radiation.

Chemical Elements A Virtual Museum under a Creative Commons Attribution 3.0 Unported License, source: https://images-of-elements.com/mendelevium.php

Bohr model of Mendelevium

Physical Propertiesmass · density · phase · crystal

Atomic Mass

258Da

Density

10.3000g/cm³

Phase (STP)

Solid

Melting Point

1100.2K

Boiling Point

—

Molar Heat

—

Crystal Structure

—

Atomic Radiiatomic · covalent · van der Waals

Atomic (Empirical)

—

Covalent

173.00pm

Van der Waals

246.00pm

Electronic Propertieselectronegativity · ionization · affinity

Electron Configuration

[Rn] 5f13 7s2

Electron Shells

2, 8, 18, 32, 31, 8, 2

Electronegativity

—

Electron Affinity

—

1st Ionization Energy

6.6kJ/mol

Oxidation States

+2, +3

Orbital DiagramAufbau · Hund's rule · Pauli exclusion

↑↓
1s2
↑↓
2s2
↑↓
↑↓
↑↓
2p6
↑↓
3s2
↑↓
↑↓
↑↓
3p6
↑↓
↑↓
↑↓
↑↓
↑↓
3d10
↑↓
4s2
↑↓
↑↓
↑↓
4p6
↑↓
↑↓
↑↓
↑↓
↑↓
4d10
↑↓
↑↓
↑↓
↑↓
↑↓
↑↓
↑↓
4f14
↑↓
5s2
↑↓
↑↓
↑↓
5p6
↑↓
↑↓
↑↓
↑↓
↑↓
5d10
↑↓
6s2
↑↓
↑↓
↑↓
6p6
↑↓
↑↓
↑↓
↑↓
↑↓
↑↓
↑
5f13
↑↓
7s2

Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 5f13 7s2Short: [Rn] 5f13 7s2

Ionization Energies (101 known)

1st6.6 kJ/mol2nd12.4 kJ/mol3rd24.3 kJ/mol4th40.0 kJ/mol5th54.1 kJ/mol6th76.0 kJ/mol7th96.0 kJ/mol8th115.1 kJ/mol9th143.9 kJ/mol10th162.0 kJ/mol11th187.0 kJ/mol12th215.0 kJ/mol13th240.0 kJ/mol14th260.0 kJ/mol15th282.0 kJ/mol16th307.0 kJ/mol17th334.0 kJ/mol18th360.0 kJ/mol19th386.0 kJ/mol20th412.0 kJ/mol21th438.0 kJ/mol22th462.0 kJ/mol23th486.0 kJ/mol24th659.0 kJ/mol25th690.0 kJ/mol26th723.0 kJ/mol27th760.0 kJ/mol28th794.0 kJ/mol29th828.0 kJ/mol30th885.0 kJ/mol31th920.0 kJ/mol32th958.0 kJ/mol33th994.0 kJ/mol34th1160.0 kJ/mol35th1210.0 kJ/mol36th1250.0 kJ/mol37th1290.0 kJ/mol38th1430.0 kJ/mol39th1480.0 kJ/mol40th1620.0 kJ/mol41th1660.0 kJ/mol42th1840.0 kJ/mol43th1930.0 kJ/mol44th2020.0 kJ/mol45th2110.0 kJ/mol46th2200.0 kJ/mol47th2290.0 kJ/mol48th2390.0 kJ/mol49th2480.0 kJ/mol50th2580.0 kJ/mol51th2680.0 kJ/mol52th2760.0 kJ/mol53th2860.0 kJ/mol54th2950.0 kJ/mol55th3050.0 kJ/mol56th3513.0 kJ/mol57th3592.0 kJ/mol58th3675.0 kJ/mol59th3762.0 kJ/mol60th3845.0 kJ/mol61th3926.0 kJ/mol62th4109.0 kJ/mol63th4194.0 kJ/mol64th4286.0 kJ/mol65th4371.0 kJ/mol66th4720.0 kJ/mol67th4800.0 kJ/mol68th4890.0 kJ/mol69th4970.0 kJ/mol70th5580.0 kJ/mol71th5680.0 kJ/mol72th5930.0 kJ/mol73th6030.0 kJ/mol74th9430.0 kJ/mol75th9620.0 kJ/mol76th9810.0 kJ/mol77th10020.0 kJ/mol78th10220.0 kJ/mol79th10410.0 kJ/mol80th10930.0 kJ/mol81th11130.0 kJ/mol82th11350.0 kJ/mol83th11560.0 kJ/mol84th12130.0 kJ/mol85th12310.0 kJ/mol86th12500.0 kJ/mol87th12680.0 kJ/mol88th14560.0 kJ/mol89th14800.0 kJ/mol90th15200.0 kJ/mol91th15400.0 kJ/mol92th31000.0 kJ/mol93th31500.0 kJ/mol94th32000.0 kJ/mol95th32500.0 kJ/mol96th39500.0 kJ/mol97th40100.0 kJ/mol98th41000.0 kJ/mol99th41548.0 kJ/mol100th162066.0 kJ/mol101th164764.0 kJ/molSuccessive Ionization Energies

Abundanceby mass

Biological Role

No biological role

Synthetic, radioactive element. No biological role.

Discovery

Discovered By

G.T.Seaborg, S.G.Tompson, A.Ghiorso, K.Street Jr.

Named By

—

Year

1955

Nuclear Data

Known Isotopes

19

Stable Isotopes

0

Stable Mass Numbers

None

Isotopes of Md19 known

NuclideZNMass (AMU)Half-lifeDecayJπAbundance
244Md101143244.081157360 msα (1%), β⁺, β⁺SF (0.14%)3+—
245Md101144245.080864380 msα (1%), β⁺7/2-—
246Md101145246.081713920 msα (1%)1-—
260Md101159260.10365027.8 dSF (1%), α (0.05%), EC (0.05%), β⁻ (0.035%)——
261Md101160261.105828Unknownα7/2-—
262Md101161262.109144UnknownSF, α——

Click any isotope for its full page with decay chain:

244Md245Md246Md247Md248Md249Md250Md251Md252Md253Md254Md255Md256Md257Md258Md259Md260Md261Md262Md
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