Chemical element · reference page

3Li

Lithium

Lithium is element 3 (Li), located in period 2, group 1 and the s block. At room temperature its reference phase is solid. Its electron configuration is [He] 2s1.

Atomic number3

Standard atomic weight[6.938, 6.997]

Group1

Period2

Blocks

Electron configuration[He] 2s1

Electronic structure

What controls its chemistry

The outer electron configuration ends in s¹. Losing that single valence electron gives a +1 ion with a filled inner-shell configuration, so lithium compounds are dominated by the +1 oxidation state.

The same outer-shell pattern is shared by the alkali metals. Down the group the outer electron is farther from the nucleus and generally easier to remove, which helps explain the high reactivity of the family.

Chemical forms

Compounds, ions and materials

The dominant chemical form is lithium in the +1 oxidation state. Ionic halides, hydroxides and oxygen-containing salts are common; the free metal is much less common in nature because it reacts readily with water, oxygen and other non-metals.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 0.534 g/cm³. The melting point is 453.6 K (180.5 °C). The boiling point is 1 603 K (1 330 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where lithium is found and used

In practice, lithium is encountered in batteries, special glasses and alloys.

In practice

Examples of real uses

Batteries

Lithium is used in selected battery chemistries, electrode materials or electrolytes. The exact role depends on the compound and cell design.

Special glasses

Lithium is added to glass to modify refractive index, colour, thermal expansion, radiation response or chemical durability.

Alloys

Lithium is added to metals to change strength, corrosion resistance, melting behaviour or high-temperature performance.

Periodic position

What its neighbours tell us

Lithium is in period 2 and group 1. In the neighbourhood shown here, beryllium is immediately to its right in the same period; hydrogen is above it and sodium below it in the same group. These positions make it possible to compare atomic size, ionisation energy and bonding behaviour with nearby elements.

Reference data

Physical and atomic properties

Classificationalkali metal

Phase at room temperatureSolid

Electron shells2 · 1

Density0.534 g/cm³

Melting point453.6 K (180.5 °C)

Boiling point1 603 K (1 330 °C)

Pauling electronegativity0.98

First ionisation energy520.2 kJ/mol

Electron affinity59.63 kJ/mol

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

The discovery of lithium is associated with Johan August Arfwedson. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is given as the interval [6.938, 6.997]. Natural samples can differ slightly in isotope proportions, so a single universal decimal value would hide real variation between materials.

Lithium has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

Elemental lithium reacts readily with moisture and can react violently with water. It is handled away from water and air under controlled conditions.