103[266]LrLawrencium
Lawrencium (Lr) — element 103actinide · period 7
Lawrencium is a chemical element with the symbol Lr and atomic number 103. It is an actinide in period 7 of the periodic table (the f-block), with a standard atomic mass of [266] u. At room temperature (25 °C) lawrencium is predicted to be a solid.
💡 Known for: Named after Ernest Lawrence, inventor of the cyclotron; it is the last of the actinides.
# Lawrencium properties
| Symbol | Lr |
|---|---|
| Atomic number | 103 |
| Atomic mass | [266] u |
| Category | actinide |
| Group | — (f-block, no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 5f¹⁴ 7s² 7p¹ |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 7s² 7p¹ |
| Electrons per shell | 2, 8, 18, 32, 32, 8, 3 |
| Protons / electrons | 103 / 103 |
| State at 25 °C | predicted solid |
| Melting point | 1900 K (1626.8 °C, 2960.3 °F) (predicted) |
| Boiling point | unknown |
| Density | — |
| Electronegativity (Pauling) | 1.3 |
| First ionization energy | 4.9 eV |
| Atomic radius | — |
| Discovered | 1961 |
Values for superheavy elements are theoretical predictions; none have been measured in bulk.
# Electron configuration of lawrencium
The electron configuration of lawrencium is [Rn] 5f¹⁴ 7s² 7p¹, written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 7s² 7p¹. Its 103 electrons fill 7 shells as 2, 8, 18, 32, 32, 8, 3, so the outermost shell holds 3 electrons. Because only a few atoms have ever been made, this configuration is a theoretical prediction.
# Related elements
NoNobeliumprevious elementRfRutherfordiumnext elementAcActiniumactinideThThoriumactinidePaProtactiniumactinideUUraniumactinideNpNeptuniumactinidePuPlutoniumactinideAmAmericiumactinideCmCuriumactinide
# Lawrencium FAQ
What is the atomic number of lawrencium?
The atomic number of lawrencium is 103: every lawrencium atom has 103 protons in its nucleus. Its symbol is Lr.
What is the atomic mass of lawrencium?
The standard atomic mass of lawrencium is [266] u (the mass number of its longest-lived isotope, since it has no stable isotopes).
What is the electron configuration of lawrencium?
Lawrencium's electron configuration is [Rn] 5f¹⁴ 7s² 7p¹ (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 7s² 7p¹), with 2, 8, 18, 32, 32, 8, 3 electrons per shell.
Is lawrencium a metal?
Yes. Lawrencium is an actinide, one of the metals.
What is the melting point of lawrencium?
Lawrencium melts at 1900 K (1626.8 °C, 2960.3 °F). These values are predictions.
What is lawrencium used for / known for?
Named after Ernest Lawrence, inventor of the cyclotron; it is the last of the actinides.