101[258]MdMendelevium
Mendelevium (Md) — element 101actinide · period 7
Mendelevium is a chemical element with the symbol Md and atomic number 101. It is an actinide in period 7 of the periodic table (the f-block), with a standard atomic mass of [258] u. At room temperature (25 °C) mendelevium is predicted to be a solid.
💡 Known for: Named after Dmitri Mendeleev, who created the periodic table in 1869.
# Mendelevium properties
| Symbol | Md |
|---|---|
| Atomic number | 101 |
| Atomic mass | [258] u |
| Category | actinide |
| Group | — (f-block, no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 5f¹³ 7s² |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹³ 6s² 6p⁶ 7s² |
| Electrons per shell | 2, 8, 18, 32, 31, 8, 2 |
| Protons / electrons | 101 / 101 |
| State at 25 °C | predicted solid |
| Melting point | 1100 K (826.9 °C, 1520.3 °F) (predicted) |
| Boiling point | unknown |
| Density | — |
| Electronegativity (Pauling) | 1.3 |
| First ionization energy | 6.58 eV |
| Atomic radius | — |
| Discovered | 1955 |
Values for superheavy elements are theoretical predictions; none have been measured in bulk.
# Electron configuration of mendelevium
The electron configuration of mendelevium is [Rn] 5f¹³ 7s², written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹³ 6s² 6p⁶ 7s². Its 101 electrons fill 7 shells as 2, 8, 18, 32, 31, 8, 2, so the outermost shell holds 2 electrons. Because only a few atoms have ever been made, this configuration is a theoretical prediction.
# Related elements
FmFermiumprevious elementNoNobeliumnext elementAcActiniumactinideThThoriumactinidePaProtactiniumactinideUUraniumactinideNpNeptuniumactinidePuPlutoniumactinideAmAmericiumactinideCmCuriumactinide
# Mendelevium FAQ
What is the atomic number of mendelevium?
The atomic number of mendelevium is 101: every mendelevium atom has 101 protons in its nucleus. Its symbol is Md.
What is the atomic mass of mendelevium?
The standard atomic mass of mendelevium is [258] u (the mass number of its longest-lived isotope, since it has no stable isotopes).
What is the electron configuration of mendelevium?
Mendelevium's electron configuration is [Rn] 5f¹³ 7s² (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹³ 6s² 6p⁶ 7s²), with 2, 8, 18, 32, 31, 8, 2 electrons per shell.
Is mendelevium a metal?
Yes. Mendelevium is an actinide, one of the metals.
What is the melting point of mendelevium?
Mendelevium melts at 1100 K (826.9 °C, 1520.3 °F). These values are predictions.
What is mendelevium used for / known for?
Named after Dmitri Mendeleev, who created the periodic table in 1869.