Lithium (Li) — Atomic Number 3

Lithium is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal that is the lightest of all metals. Like all alkali metals, it is highly reactive and must be stored under oil. Its name comes from Greek lithos meaning “stone” — it was discovered in a mineral, unlike sodium and potassium which were found in plants.

At a Glance

Discovery

Discovered in 1817 by Swedish chemist Johan Arfwedson while analysing the mineral petalite. First isolated as the pure metal in 1821 by William Brande via electrolysis.

Chemical Properties

Lithium is the least reactive alkali metal, though still highly reactive. It forms Li⁺ ions (configuration 2, like helium).

Key Reactions

1. With water: $2\text{Li}+2{\text{H}}_2\text{O}\to 2\text{LiOH}+{\text{H}}_2$ — fizzes steadily, does NOT melt or ignite (unlike Na and K)
2. With oxygen: $4\text{Li}+{\text{O}}_2\to 2{\text{Li}}_2\text{O}$
3. With chlorine: $2\text{Li}+{\text{Cl}}_2\to 2\text{LiCl}$
4. With nitrogen: $6\text{Li}+{\text{N}}_2\to 2{\text{Li}}_3\text{N}$ — unique among alkali metals

Characteristic Test

Flame test: Crimson red

Compounds & Uses

• Lithium-ion batteries — phones, laptops, electric vehicles (~74% of demand)
• Alloys — lightweight aircraft components
• Lubricating greases — lithium stearate

IGCSE Essentials

1. Flame test: crimson red
2. Least reactive alkali metal — reactivity increases down Group 1
3. Stored under oil
4. Forms Li⁺ (loses 1 electron)
5. Reaction with water is the least vigorous of Group 1

Sources

• Lithium — Wikipedia
• Lithium — Ptable.com
• Lithium — RSC Periodic Table