Lawrencium (Lr)
Actinide · f-block · period 7
Never seen; the last of the actinide row.
Lawrencium (symbol Lr) is chemical element number 103, a actinide in the actinide series (f-block), period 7 of the periodic table. Its standard atomic weight is (266) and its electron configuration is [Rn] 5f14 7s2 7p1. Its state at room temperature is unknown, and it is radioactive. Named after Ernest Lawrence, inventor of the cyclotron.
Properties
| Atomic number | 103 |
|---|---|
| Atomic mass | (266) |
| Category | Actinide |
| Block | f-block |
| Group · Period | f-block series · 7 |
| Electron configuration | [Rn] 5f14 7s2 7p1 |
| Electrons per shell | 2, 8, 18, 32, 32, 8, 3 |
| State at 25 °C | unknown |
| Melting point | 1900 K |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | 1.3 |
| Radioactive | Yes — no stable isotope |
| Origin | synthetic |
| Discovered | 1961 · Ghiorso et al. (Berkeley) |
Key facts about Lawrencium
- Named after Ernest Lawrence, inventor of the cyclotron.
- Closes the actinide series.
- Its outer electron unexpectedly goes into a 7p rather than a 6d orbital — a relativistic effect.
- Fewer than a hundred atoms have been studied in total.
What Lawrencium is used for
None — research only.
Where it sits in the periodic table
Lawrencium is in the actinide series, period 7, of the f-block. Its electron configuration [Rn] 5f14 7s2 7p1 means its outermost shell holds 3 electrons, which is what places it here and explains much of its chemistry. See Lawrencium on the interactive table →
Lawrencium — frequently asked questions
What is Lawrencium used for?
None — research only.
Is Lawrencium radioactive?
Yes. Lawrencium has no stable isotope, so every form of it is radioactive.
What is the electron configuration of Lawrencium?
Lawrencium has the electron configuration [Rn] 5f14 7s2 7p1, which is 2, 8, 18, 32, 32, 8, 3 electrons per shell.
What group and period is Lawrencium in?
Lawrencium is in the actinide series (f-block), period 7, in the f-block. Its outer shell holds 3 electrons.
Who discovered Lawrencium?
Lawrencium was discovered in 1961 by Ghiorso et al. (Berkeley).