Moleculium

Atomic number 101

Md

Mendelevium

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101 electrons in 7 shells: 2, 8, 18, 32, 31, 8, 2.

Shells are a teaching model: an electron does not travel on a ring at a fixed distance.

Bohr model of the mendelevium atom: a nucleus drawn in the CPK colour for mendelevium, surrounded by 7 electron shells drawn as rings holding 2, 8, 18, 32, 31, 8 and 2 electrons. The viewer also draws the shape of mendelevium's outer orbitals, computed for a one-electron atom and shown without a scale.
Category
Actinide
Period
7
Block
f
Atomic mass
258.09843 Da (longest-lived isotope)
Electron configuration
[Rn] 5f13 7s2
Phase at 25 °C
solid
Melting point
827 °C
Electronegativity (Pauling)
1.3

Neighbours in the table

Fm , Fermium, actinide No , Nobelium, actinide

Properties

Properties of mendelevium Standard atomic weights from IUPAC/CIAAW (abridged, 2024); other values from PubChem's periodic table, kelvin converted to °C.
Property Value Unit Source
Atomic number 101
Atomic mass 258.09843   Da Da PubChem, longest-lived isotope
Melting point 827   °C °C Los Alamos: 827 °C
Electronegativity (Pauling) 1.3
Electron configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f13
Phase at 25 °C solid

This element has no standard atomic weight; the atomic mass shown is that of its longest-lived isotope, as PubChem gives it.

Sources

  1. PubChem, element 101 (mendelevium)
  2. Periodic-Table-JSON by Bowserinator (CC BY-SA 3.0)