---
title: "Lawrencium (Lr) — element 103"
description: "Lawrencium is element 103, symbol Lr, most stable isotope 266. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/lawrencium/
site: "At One Place"
---

# Lawrencium (Lr)

**Lawrencium — element 103: Lr**

[266] · Actinide · period 7

Lawrencium breaks the pattern every other actinide follows: its outermost electron sits in a 7p orbital rather than the expected 6d, because relativistic effects have pulled the 7p level below the 6d one. That was predicted for decades and confirmed in 2015, when a Japanese team measured lawrencium's first ionisation energy — the lowest of any actinide, and low enough to settle the question — using just a few atoms at a time. It is the last actinide, and on IUPAC's 2021 recommendation it belongs in group 3 alongside lutetium.

## Properties

- **Atomic number:** 103
- **Symbol:** Lr
- **Mass number of most stable isotope:** [266]
- **Category:** Actinide
- **Period:** 7
- **Block:** p-block
- **Electron configuration:** [Rn] 7s² 5f¹⁴ 7p¹
- **Electrons per shell:** 2, 8, 18, 32, 32, 8, 3
- **Oxidation states:** +3
- **Discovered:** 1961 by Albert Ghiorso and colleagues at Berkeley, with confirming work at Dubna

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 7p¹
- **Noble gas shorthand:** [Rn] 7s² 5f¹⁴ 7p¹
- **Shells:** K: 2 · L: 8 · M: 18 · N: 32 · O: 32 · P: 8 · Q: 3

## What it is used for

- Research only; no application outside the laboratory

## Hazards

- Intensely radioactive; exists only as individual atoms in an accelerator

> Anomalous electron configuration: [Rn] 7s² 5f¹⁴ 7p¹ rather than the 6d¹ that periodic position predicts, and that many older tables still print. Melting point, boiling point, density and electronegativity are omitted: no measured values exist. The mass given is the mass number of lawrencium-266, the longest-lived at about 11 hours.

> Several physical properties are not listed for lawrencium because no bulk sample has ever existed. Only a handful of atoms have been produced, often with half-lives measured in seconds, so published melting points and densities for elements in this range are calculations rather than measurements. They are omitted rather than presented as observed values.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 101 | Mendelevium | Md | [258] |
| 102 | Nobelium | No | [259] |
| 103 | Lawrencium ← | Lr | [266] |
| 104 | Rutherfordium | Rf | [267] |
| 105 | Dubnium | Db | [268] |

## Common questions

### What is the atomic number of lawrencium?

103. That is the number of protons in its nucleus, which is what defines the element.

### What is the symbol for lawrencium?

Lr.

### What is the electron configuration of lawrencium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 7p¹, or [Rn] 7s² 5f¹⁴ 7p¹ in noble-gas shorthand.

## Related pages

- [Mendelevium (Md)](https://atoneplace.net/element/mendelevium/)
- [Nobelium (No)](https://atoneplace.net/element/nobelium/)
- [Rutherfordium (Rf)](https://atoneplace.net/element/rutherfordium/)
- [Dubnium (Db)](https://atoneplace.net/element/dubnium/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)