Element 101 · Actinide
Mendelevium (Md) — Element 101
Dmitri Mendeleev
Mendelevium (Md) is an actinide in Period 7 (f-block) of the periodic table with atomic number 101, standard atomic weight [258] u, and ground-state electron configuration [Rn] 5f¹³ 7s². At standard temperature and pressure it is classified as a short-lived synthetic nuclide with 3 valence electrons and common oxidation states +3, +2.
Research only
What are the atomic properties and physical constants of Mendelevium?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 101
- Standard atomic mass
- [258] u
- Chemical family
- Actinide
- Ground-state configuration
- [Rn] 5f¹³ 7s²
- Electrons per shell
- 2, 8, 18, 32, 31, 8, 2
- Valence electrons
- 3
- Common ion charges / oxidation states
- +3, +2
- Phase at STP
- Synthetic
- Pauling electronegativity
- 1.30 Pauling
- First ionization energy
- 635 kJ/mol
- Atomic radius
- —
- Melting point
- 827 °C
- Boiling point
- —
- Discovery year
- 1955
- Table coordinate
- Period 7, f-block
- Radioactivity
- Radioactive (no stable isotopes)
How are electrons arranged across Mendelevium’s shells?
A neutral Mendelevium atom contains 101 electrons distributed across 7 occupied principal energy shells ([Rn] 5f¹³ 7s²). The table below compares Mendelevium’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in Md | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 8 e⁻ | 8 e⁻ |
| n = 3 | M | 18 e⁻ | 18 e⁻ |
| n = 4 | N | 32 e⁻ | 32 e⁻ |
| n = 5 | O | 31 e⁻ | 50 e⁻ |
| n = 6 | P | 8 e⁻ | 72 e⁻ |
| n = 7 | Q | 2 e⁻ | 98 e⁻ |
Frequently Asked Questions about Mendelevium (Md)
What is the atomic mass and atomic number of Mendelevium (Md)?
Mendelevium (Md) has atomic number Z = 101 (101 protons in its nucleus) and an IUPAC standard atomic weight of [258] u. It sits in Period 7 in the f-block and is classified as an actinide.
What is the ground-state electron configuration of Mendelevium?
The neutral ground-state electron configuration of Mendelevium (Z = 101) is [Rn] 5f¹³ 7s². Across its 7 occupied principal shells (n = 1 to n = 7), the electrons per shell are 2, 8, 18, 32, 31, 8, 2, with 3 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Mendelevium?
Mendelevium commonly forms +3, +2 oxidation states or ion charges in compounds. Its Pauling electronegativity is 1.30 and its first ionization energy is 635 kJ/mol.
When was Mendelevium discovered and what is it used for?
Mendelevium was discovered in 1955 (Dmitri Mendeleev). Research only
How does Mendelevium compare to neighboring elements?
Other actinide elements: