Mendelevium
Mendelevium (Md, atomic number 101) is a Period 7 actinide (f-block, 258 u). Named after Dmitri Mendeleev and first synthesized one atom at a time (17 atoms of ²⁵⁶Md) by bombarding einsteinium-253 with alpha particles in the Berkeley 60-inch cyclotro
Mendelevium is a chemical element on the periodic table with the atomic symbol Md, atomic number 101, and standard atomic weight 258 u. Classified as a Actinide within Group 3 and Period 7 (f-block), mendelevium possesses a ground-state electron configuration of [Rn] 5f13 7s2 distributed across 7 concentric Bohr electron shells (2 · 8 · 18 · 32 · 31 · 8 · 2) with 2 outer-shell electrons. Named after Dmitri Mendeleev and first synthesized one atom at a time (17 atoms of ²⁵⁶Md) by bombarding einsteinium-253 with alpha particles in the Berkeley 60-inch cyclotron.
⚛️ Interactive Periodic Table Lab: Explore Mendelevium (Md, Z = 101) in the CRV Science Dynamic Periodic Table & Bohr Orbital Lab to visualize its animated 2 · 8 · 18 · 32 · 31 · 8 · 2 electron shells, simulate live phase transitions from 0 K to 6,000 K, and compare periodic heatmaps across all 118 IUPAC elements.
Atomic Structure and Periodic Trends: How Do Quantum Orbitals Define Mendelevium?
Electron Shell Architecture and Ground-State Configuration
A neutral atom of mendelevium contains 101 protons in its atomic nucleus balanced by 101 electrons occupying quantized atomic orbitals. In the Bohr-Sommerfeld and quantum-mechanical orbital models, these electrons populate 7 principal energy shells (K (n=1): 2e−, L (n=2): 8e−, M (n=3): 18e−, N (n=4): 32e−, O (n=5): 31e−, P (n=6): 8e−, Q (n=7): 2e−), terminating in the seven-orbital f-subshell manifold (azimuthal quantum number l = 3) with ground-state configuration [Rn] 5f13 7s2. Removing the most loosely bound valence electron from an isolated gaseous mendelevium atom requires a first ionization energy of 635 kJ/mol, while its tendency to attract shared bonding electrons is quantified by a Pauling electronegativity of 1.30.
Periodic Table Position and Neighboring Elements
Within the periodic table, Mendelevium occupies Period 7, Group 3 of the f-block (Actinides). Along Period 7, it is flanked by Fermium (Fm, Z = 100) and Nobelium (No, Z = 102). Vertically within its periodic family, Mendelevium shares valence orbital symmetry and homologous chemical trends with Actinium (Ac), Thorium (Th), Protactinium (Pa), Uranium (U). Learners can interactively compare Mendelevium's orbital radii, ionization energy, and Pauling electronegativity against all neighboring elements in the Dynamic Periodic Table Lab.
Physical and Thermodynamic Properties: How Does Mendelevium Behave Across Temperature Regimes?
Standard Phase, Melting Point, and Boiling Point Dynamics
At standard ambient temperature and pressure (298.15 K / 25 °C, 1 atm), elemental mendelevium exists as a crystalline solid. As thermal energy increases, its crystal or molecular lattice undergoes solid-to-liquid fusion at a melting point of 1,100 K (+826.85 °C / +1520.3 °F) and transitions to the vapor phase at a normal boiling point of Unknown (predicted synthetic regime), spanning a liquid thermodynamic range of N/A (sublimes or synthetic regime). In the CRV Science Dynamic Periodic Table, dragging the live temperature slider between absolute zero (0 K) and solar-photosphere temperatures (6,000 K) dynamically tracks Mendelevium's state transitions in real time alongside enthalpy and entropy phase equilibria.
Quantitative Atomic and Thermodynamic Parameter Matrix
| Parameter | Quantitative Value / Formula | Physical / Quantum Basis | Comparative Context in Group 3 / Period 7 |
|---|---|---|---|
| Atomic Number & Symbol | Z = 101 (Md) | 101 nuclear protons; nuclear charge +101e | Located in Period 7, Group 3 (f-block) |
| Standard Atomic Weight | 258 u (g/mol) | Abundance-weighted isotopic nucleon mass | ~157 neutrons in dominant/reference mass number |
| Electron Configuration | [Rn] 5f13 7s2 | Shells: 2 · 8 · 18 · 32 · 31 · 8 · 2 (2 outer-shell e−) | Actinides valence orbital architecture |
| Electronegativity & Ionization | χ = 1.30; IE1 = 635 kJ/mol | Pauling bond polarity scale & first valence ionization enthalpy | Governs covalent vs. ionic bond character |
| Melting & Boiling Points | MP: 1100 K; BP: Unknown | Cohesive lattice energy and intermolecular forces | STP (298 K) phase: SOLID (Liquid range: N/A (sublimes or synthetic regime)) |
| Principal Oxidation States | +3, +2 | Valence electron donation, sharing, or acceptance | Discovered / First Isolated: 1955 |
Chemical Reactivity, Bonding, and Oxidation States: How Does Mendelevium Form Compounds?
Characteristic Oxidation States and Coordination Chemistry
As a 5f-block actinide element with radially extended 5f, 6d, and 7s valence orbitals and an unstable heavy nucleus, it combines multi-valent actinide coordination chemistry with radioactive alpha, beta, or spontaneous-fission decay. In chemical compounds, mendelevium exhibits characteristic oxidation states of +3, +2. Depending on the electronegativity difference (Δχ) of its bonding partners—such as Oxygen (χ = 3.44), Fluorine (χ = 3.98), Chlorine (χ = 3.16), Nitrogen (χ = 3.04), Carbon (χ = 2.55), or Hydrogen (χ = 2.20)—mendelevium forms redox-specific oxides, halides, hydrides, or coordination complexes governed by Gibbs free energy (ΔG = ΔH − TΔS).
Nucleosynthesis, Discovery History, and Elemental Origins
First identified or isolated in 1955, Mendelevium carries a distinct cosmological and geochemical signature. As a synthetic transuranic element (Z = 101), mendelevium does not persist in primordial terrestrial minerals and is produced atom-by-atom in nuclear reactors or heavy-ion particle accelerators.
Biological Role and Scientific Applications: Why Is Mendelevium Important in Nature and Technology?
Biochemical Classification: Abiotic / Technological / Synthetic
In comparative biochemistry and systems physiology, Mendelevium is classified as Abiotic / Technological / Synthetic. No known essential biological role; important in planetary geochemistry, astrophysics, materials science, or nuclear physics. Across terrestrial and marine ecosystems, its chemical speciation interacts with thermodynamics, enthalpy, entropy, chemistry.
Key Mechanistic Functions and Technological Uses
Named after Dmitri Mendeleev and first synthesized one atom at a time (17 atoms of ²⁵⁶Md) by bombarding einsteinium-253 with alpha particles in the Berkeley 60-inch cyclotron. Researchers and students can further investigate Mendelevium's functional role alongside all 118 elements by launching the Interactive Periodic Table & Element Detective Lab on CRV Science Learn.
Frequently Asked Scientific Questions
What is the electron configuration and valence shell structure of Mendelevium (Md)?
Mendelevium (atomic number Z = 101) has the ground-state electron configuration [Rn] 5f13 7s2, distributing its 101 electrons across 7 shells as 2 · 8 · 18 · 32 · 31 · 8 · 2. Its outermost shell contains 2 electrons, placing Mendelevium in Group 3, Period 7 (f-block) as a member of the Actinides. You can watch these 101 electrons orbit the nucleus in real time in the Dynamic Periodic Table Bohr Lab.
What phase of matter is Mendelevium at room temperature, and when does it melt or boil?
At standard room temperature (298 K / 25 °C) and 1 atm pressure, Mendelevium is a crystalline solid. It melts at 1,100 K (+826.85 °C / +1520.3 °F) and boils at Unknown (predicted synthetic regime). Using the 0–6,000 K temperature slider in the Interactive Periodic Table, you can observe Mendelevium's exact solid, liquid, and gas transitions relative to all other elements.
How does Mendelevium function in biochemistry, materials science, and technology?
Named after Dmitri Mendeleev and first synthesized one atom at a time (17 atoms of ²⁵⁶Md) by bombarding einsteinium-253 with alpha particles in the Berkeley 60-inch cyclotron. In biological systems, it is categorized under Abiotic / Technological / Synthetic, with principal oxidation states of +3, +2 and a first ionization energy of 635 kJ/mol.