Lawrencium (Lr): electron configuration, atomic mass and facts
Lawrencium (Lr) is element 103 of the periodic table, an actinide in period 7 (f-block). Its electron configuration is [Rn] 5f14 7s2 7p1, with electrons arranged in shells 2, 8, 18, 32, 32, 8, 3, and its most stable isotope has mass number 266.
▶ Watch Lawrencium’s electrons orbit in the interactive periodic tableLawrencium at a glance
| Symbol | Lr |
|---|---|
| Atomic number | 103 |
| Atomic mass | [266] u (most stable isotope) |
| Category | Actinide |
| Group | f-block (no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 7s2 7p1 |
| Noble-gas shorthand | [Rn] 5f14 7s2 7p1 |
| Electrons per shell | 2, 8, 18, 32, 32, 8, 3 |
| Electronegativity (Pauling) | 1.3 |
| State at 20 °C | solid |
Where is Lawrencium on the periodic table?
Lawrencium is in period 7 of the f-block, the actinide row printed below the main table. It has 7 electron shells, and this row is where the 5f subshell fills (its own configuration is an exception, explained below).
How to work out the electron configuration of Lawrencium
Put 103 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s² (12), 3p⁶ (18), 4s² (20), 3d¹⁰ (30), 4p⁶ (36), 5s² (38), 4d¹⁰ (48), 5p⁶ (54), 6s² (56), 4f¹⁴ (70), 5d¹⁰ (80), 6p⁶ (86), 7s² (88), 5f¹⁴ (102), 6d¹ (103). Lawrencium is one of the exceptions to this filling order: experiments show its ground state is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 7p¹ rather than 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹, because the neighbouring subshells are so close in energy. In shorthand, [Rn] stands for the 86 electrons of radon, giving [Rn] 5f¹⁴ 7s² 7p¹.
How electronegative is Lawrencium?
Lawrencium has a Pauling electronegativity of 1.3, ranking 62 of the 100 elements with a known value (fluorine is highest at 3.98). That is low: it tends to give up electrons and form positive ions.
Frequently asked questions
What is the electron configuration of Lawrencium?
The electron configuration of Lawrencium (Lr) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 7s2 7p1. In noble-gas shorthand it is written [Rn] 5f14 7s2 7p1.
How many electrons does Lawrencium have in each shell?
Lawrencium has 103 electrons arranged in shells as 2, 8, 18, 32, 32, 8, 3.
What is the atomic mass of Lawrencium?
Lawrencium has no stable isotopes. Its most stable isotope has a mass number of 266.
Is Lawrencium a metal?
Yes. Lawrencium is an actinide.
Explore nearby elements
More actinides: Berkelium, Californium, Einsteinium, Fermium, Mendelevium, Nobelium. See all elements on the periodic table.