Mendelevium (Md)
Actinide · f-block · period 7
Never seen; studied one atom at a time.
Mendelevium (symbol Md) is chemical element number 101, a actinide in the actinide series (f-block), period 7 of the periodic table. Its standard atomic weight is (258) and its electron configuration is [Rn] 5f13 7s2. Its state at room temperature is unknown, and it is radioactive. Named after Dmitri Mendeleev, father of the periodic table.
Properties
| Atomic number | 101 |
|---|---|
| Atomic mass | (258) |
| Category | Actinide |
| Block | f-block |
| Group · Period | f-block series · 7 |
| Electron configuration | [Rn] 5f13 7s2 |
| Electrons per shell | 2, 8, 18, 32, 31, 8, 2 |
| State at 25 °C | unknown |
| Melting point | 1100 K |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | 1.3 |
| Radioactive | Yes — no stable isotope |
| Origin | synthetic |
| Discovered | 1955 · Ghiorso, Harvey, Choppin, Thompson & Seaborg |
Key facts about Mendelevium
- Named after Dmitri Mendeleev, father of the periodic table.
- The first element made and identified one atom at a time.
- The discovery experiment produced only about 17 atoms — yet that was enough to study its chemistry.
- Its chemistry showed the actinide series behaves as predicted.
What Mendelevium is used for
None — research only.
Where it sits in the periodic table
Mendelevium is in the actinide series, period 7, of the f-block. Its electron configuration [Rn] 5f13 7s2 means its outermost shell holds 2 electrons, which is what places it here and explains much of its chemistry. See Mendelevium on the interactive table →
Mendelevium — frequently asked questions
What is Mendelevium used for?
None — research only.
Is Mendelevium radioactive?
Yes. Mendelevium has no stable isotope, so every form of it is radioactive.
What is the electron configuration of Mendelevium?
Mendelevium has the electron configuration [Rn] 5f13 7s2, which is 2, 8, 18, 32, 31, 8, 2 electrons per shell.
What group and period is Mendelevium in?
Mendelevium is in the actinide series (f-block), period 7, in the f-block. Its outer shell holds 2 electrons.
Who discovered Mendelevium?
Mendelevium was discovered in 1955 by Ghiorso, Harvey, Choppin, Thompson & Seaborg.