103Lr[266]
Lawrencium (Lr)
Element 103 · Actinide
Lawrencium (Lr) is a chemical element with atomic number 103. It is classified as an actinide in period 7 of the periodic table (the f-block). Its most stable known isotope has mass number 266 and its ground-state electron configuration is [Rn] 5f¹⁴ 7s² 7p¹.
Lawrencium facts
| Atomic number (Z) | 103 |
|---|---|
| Symbol | Lr |
| Mass number of most stable isotope | [266] |
| Category | Actinide |
| Group | — (f-block) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 5f¹⁴ 7s² 7p¹ |
| Electronegativity (Pauling) | — |
| State at 20 °C | Unknown (synthetic) |
| Protons / electrons | 103 / 103 |
| Neutrons (most common isotope, approx.) | 163 |
| Molar mass | 266 g/mol |