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Mendelevium

Element 101 · Actinide

Specimen

Atomic number
101
Atomic mass
[258]
State at room temperature
Solid
Melting point
826.9 °C
Boiling point
Unknown
Density
Unknown
Discovered
1955

Mass number of the longest-lived isotope, from IUPAC.1 Other physical data from PubChem.2

Can I eat it?

In food and water
Never made in amounts you could eat. Laboratories make mendelevium a few atoms at a time. The first experiment in 1955 made 17 atoms. 3

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The atom

Md
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 32
5 (O) 31
6 (P) 8
7 (Q) outermost 2
Total101

Configuration [Rn] 5f¹³ 7s²

5f ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑
7s ↑ ↓
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 101 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Rn core, with one arrow per electron.

Related elements

Actinides
Ac Actinium Th Thorium Pa Protactinium U Uranium Np Neptunium Pu Plutonium Am Americium Cm Curium Bk Berkelium Cf Californium Es Einsteinium Fm Fermium No Nobelium Lr Lawrencium

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Sources

  1. 1

    IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Radioactive Elements .

    Mass number and half-life of the longest-lived isotope of the 34 elements with no standard atomic weight.

  2. 2

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  3. 3

    Royal Society of Chemistry, Periodic Table, 2026. Mendelevium - Element information, properties and uses .

    Reference page; its Biological role and Natural abundance sections are quoted.

    • produce just a few atoms - 17, to be precise - of mendelevium.