Lawrencium (Lr)
Element 103 · Actinide · atomic mass [266] u · f-block, period 7
Electron shells: 2, 8, 18, 32, 32, 9, 2
Lawrencium closes the actinide series and exists only as a handful of fleeting atoms. IUPAC now recommends it, with lutetium, for group 3 of the table.
Measuring lawrencium's ionisation energy in 2015 took years of work on single atoms at a time.
- Atomic number
- 103
- Atomic mass
- [266] u
- Electron configuration
- [Rn] 7s² 5f¹⁴ 6d¹
- Group · period · block
- f-block · 7 · f
- Oxidation states
- +3
- Electronegativity
- 1.3 (Pauling)
- Melting point
- 1,627 °C
- Boiling point
- —
- Density
- Not measured
- State at 20 °C
- Solid
- Appearance
- Unknown; presumed metallic
- Discovered
- Albert Ghiorso and colleagues; Dubna, 1961
103 protons, and 103 electrons when neutral
Mass number of the longest-lived isotope — no standard atomic weight exists
Shown in the strip below the table
What Lawrencium is used for
- Scientific research only
Atomic structure of Lawrencium
A neutral lawrencium atom has 103 protons and 103 electrons. Its most common isotope carries about 163 neutrons, which is where the mass number 266 comes from. Change the neutron count and you have a different isotope of lawrencium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 32, 9, 2. In orbital notation that is [Rn] 7s² 5f¹⁴ 6d¹. As a f-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Lawrencium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Lawrencium sits in the periodic table
The second f-block row, elements 89-103. All are radioactive, and everything past uranium is essentially man-made.
- One proton lighter: Nobelium.
- One proton heavier: Rutherfordium.
Discovery and naming
Lawrencium was discovered by Albert Ghiorso and colleagues; Dubna in 1961. Its name comes from Ernest Lawrence, inventor of the cyclotron, which is also why its symbol (Lr) does not match its English name.
Every isotope of lawrencium is radioactive, so it has no standard atomic weight. Periodic tables show the mass number of its longest-lived isotope in square brackets instead.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Lawrencium?
Lawrencium has no stable isotope, so it has no standard atomic weight. Periodic tables instead show 266 in square brackets — the mass number of its longest-lived isotope.
How many protons, neutrons and electrons does Lawrencium have?
Lawrencium has 103 protons, because the atomic number is the proton count and that is what makes an atom Lawrencium at all. A neutral Lawrencium atom has the same number of electrons, 103. The neutron count varies by isotope; the most common one has about 163, since 266 − 103 = 163.
What is the electron configuration of Lawrencium?
The electron configuration of Lawrencium is [Rn] 7s² 5f¹⁴ 6d¹. Its electrons are arranged 2, 8, 18, 32, 32, 9, 2 across 7 shells.
Is Lawrencium a metal?
Yes. Lawrencium is classified as a actinide, on the metallic side of the table.
What group and period is Lawrencium in?
Lawrencium sits in the f-block strip below the main table, in period 7, among the actinides. Elements in that strip are not given a group number in the standard 18-column layout.
What is the charge of Lawrencium?
Lawrencium most commonly forms a 3+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound.
What is the melting point of Lawrencium?
Lawrencium melts at 1,627 °C. That puts it in the solids at everyday temperatures.
What is Lawrencium used for?
Scientific research only. Lawrencium closes the actinide series and exists only as a handful of fleeting atoms.
Who discovered Lawrencium, and where does its name come from?
Lawrencium (Lr) was discovered by Albert Ghiorso and colleagues; Dubna in 1961. The name comes from Ernest Lawrence, inventor of the cyclotron.
Is Lawrencium radioactive?
Yes. Every isotope of Lawrencium is radioactive — it has no stable form at all, which is why the periodic table shows its mass in square brackets rather than as a standard atomic weight.