Lithium (Li)
Element 3 · Alkali metal · atomic mass 6.94 u · group 1, period 2
Electron shells: 2, 1
Lithium is the lightest metal and the least dense solid element, soft enough to cut with a knife. Its eagerness to give up an electron makes it the backbone of rechargeable battery chemistry.
Lithium is light enough to float on water — though it reacts with it while doing so.
- Atomic number
- 3
- Atomic mass
- 6.94 u
- Electron configuration
- [He] 2s¹
- Group · period · block
- 1 · 2 · s
- Oxidation states
- +1
- Electronegativity
- 0.98 (Pauling)
- Melting point
- 181 °C
- Boiling point
- 1,342 °C
- Density
- 0.534 g/cm³
- State at 20 °C
- Solid
- Appearance
- Soft, silvery-white metal
- Discovered
- Johan August Arfwedson, 1817
3 protons, and 3 electrons when neutral
IUPAC interval [6.938, 6.997]
Alkali metals
What Lithium is used for
- Lithium-ion batteries
- Heat-resistant glass and ceramics
- Bipolar disorder medication
- Aluminium alloys for aircraft
Atomic structure of Lithium
A neutral lithium atom has 3 protons and 3 electrons. Its most common isotope carries about 4 neutrons, which is where the mass number 7 comes from. Change the neutron count and you have a different isotope of lithium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 1. In orbital notation that is [He] 2s¹, leaving 1 valence electron in the outer shell — the ones that do the chemistry.
3D electron orbitals
See where Lithium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Lithium sits in the periodic table
Group 1 metals with a single outer electron. Soft, low-melting and so reactive they are stored under oil — reactivity increases as you go down the group.
Discovery and naming
Lithium was discovered by Johan August Arfwedson in 1817. Its name comes from Greek lithos, "stone".
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 Lithium?
The standard atomic weight of Lithium is 6.94 u. Because the natural isotope mix varies between sources, IUPAC publishes it as the interval [6.938, 6.997], and 6.94 is the conventional single value to use in calculations.
How many protons, neutrons and electrons does Lithium have?
Lithium has 3 protons, because the atomic number is the proton count and that is what makes an atom Lithium at all. A neutral Lithium atom has the same number of electrons, 3. The neutron count varies by isotope; the most common one has about 4, since 7 − 3 = 4.
What is the electron configuration of Lithium?
The electron configuration of Lithium is [He] 2s¹. Its electrons are arranged 2, 1 across 2 shells.
Is Lithium a metal?
Yes. Lithium is classified as a alkali metal, on the left side of the table.
What group and period is Lithium in?
Lithium is in group 1 (the alkali metals), period 2, in the s-block. The group is its column and the period is its row.
What is the charge of Lithium?
Lithium most commonly forms a 1+ ion. It has 1 electron in its outer shell and loses it readily, which is what the group number tells you.
What is the melting point of Lithium?
Lithium melts at 181 °C and boils at 1,342 °C. That puts it in the solids at everyday temperatures.
What is Lithium used for?
Lithium-ion batteries, Heat-resistant glass and ceramics, Bipolar disorder medication, Aluminium alloys for aircraft. Lithium is the lightest metal and the least dense solid element, soft enough to cut with a knife.
Who discovered Lithium, and where does its name come from?
Lithium (Li) was discovered by Johan August Arfwedson in 1817. The name comes from Greek lithos, "stone".