Quick answerMendelevium (Md) is an actinide with atomic number 101 and a mass number of 258 (the most stable isotope), in period 7. It was discovered by Albert Ghiorso and colleagues in 1955. It is used for actinide research and studying heavy-element chemistry. Its electron configuration is [Rn] 5f13 7s2.
Mendelevium was the first element made one atom at a time, named for the father of the periodic table.
Key facts
| Symbol | Md |
|---|---|
| Atomic number | 101 |
| Atomic mass | [258] — mass number of the most stable isotope |
| Category | actinide |
| Group | — (f-block element, no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 5f13 7s2 |
| Discovered | Albert Ghiorso and colleagues, 1955 |
| Uses | actinide research, studying heavy-element chemistry |
Quick quiz
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Keep exploring
- Periodic table — all 118 elements
- Neptunium (Np) — another actinide, atomic number 93
- Plutonium (Pu) — another actinide, atomic number 94
- Americium (Am) — another actinide, atomic number 95
- Curium (Cm) — another actinide, atomic number 96
- Berkelium (Bk) — another actinide, atomic number 97
- Californium (Cf) — another actinide, atomic number 98
- Einsteinium (Es) — another actinide, atomic number 99
- Fermium (Fm) — another actinide, atomic number 100
- Nobelium (No) — another actinide, atomic number 102
- Lawrencium (Lr) — another actinide, atomic number 103
- All actinide elements — on the periodic table
Sources & last updated
- CIAAW — Standard Atomic Weights
- PubChem Periodic Table
- Wikipedia — Timeline of chemical element discoveries
Last updated: . Figures are shown with their year; where sources disagree, the value is left out rather than estimated.