Average mass of an atom in unified atomic mass units (1 u is 1/12 of the mass of a carbon-12 atom). Accounts for the natural mix of the element’s isotopes.
Number of the vertical column, 1 to 18 in IUPAC numbering. Elements in a group share the same outer-shell layout, so their properties are alike.
Number of the horizontal row. Usually equal to the number of electron shells in the atom; palladium is the exception, with four shells in period 5.
The subshell (s, p, d or f) that receives the last electrons in the usual filling order; it divides the table into four blocks. Real atoms sometimes differ: lanthanum starts the f-block but has no f electrons.
[He] 2s¹
How electrons are arranged in subshells. The bracket stands for the previous noble gas; the superscript is the number of electrons in a subshell.
2, 1
Number of electrons in each shell, from the nucleus outwards.
180.5 °C (453.65 K)
Temperature at which the solid turns liquid at standard pressure. Helium, carbon and arsenic do not melt at normal pressure: helium needs about 25 atm, carbon and arsenic turn straight into vapour.
1,342 °C (1,615 K)
Temperature at which the liquid boils at standard pressure. For carbon and arsenic, the temperature at which the solid turns straight into vapour (sublimation).
0.534 g/cm³
Mass of one cubic centimetre of the substance. For gases, at 0 °C and standard pressure.
0.98 Pauling
How strongly an atom pulls electrons towards itself in a chemical bond. On the Pauling scale it runs from 0.79 for caesium to 3.98 for fluorine.
5.392 eV
Energy needed to remove the most loosely bound electron from an atom. The lower it is, the more easily the element gives up an electron, which is typical of metals.
0.618 eV
Energy released when a neutral atom gains an electron. Highest for the halogens. Noble gases, nitrogen and some metals form no stable negative ion.
128 pm
Half the length of a single covalent bond between two atoms of the element. It shows the size of an atom inside a molecule or crystal: 76 pm for carbon, 132 pm for iron.
+1
Charges the atom would have in its compounds if all its bonds were ionic; the main ones are listed.
Lithium (Li) is a chemical element with atomic number 3. It sits in group 1 and period 2 of the periodic table, in the s-block. It is an alkali metal. At room temperature it is a solid. Its standard atomic weight is 6.94.
Origin of the name
The name comes from Greek líthos, ‘stone’. Johan August Arfwedson found the element in 1817 in the mineral petalite, and his teacher Jöns Jacob Berzelius called it lithion: unlike sodium and potassium, which were known from plant ashes and animal matter, it had been discovered in a stone.
Where is lithium found?
Lithium is too reactive to occur free in nature. It is spread thinly through many rocks and is mined from ores such as spodumene, lepidolite and petalite, and from the brine of salt lakes, which is pumped up and left to evaporate in the sun.
What is lithium used for?
Most lithium today goes into lithium-ion batteries for phones, laptops and electric cars. It also makes glass and ceramics resistant to heat, thickens lubricating greases that work in heat and cold, and lithium carbonate is a medicine for bipolar disorder.
Interesting facts
Lithium is the lightest metal: it is only about half as dense as water and floats on it.
Lithium salts colour a flame crimson red.
Lithium reacts with water, but much more calmly than sodium or potassium.
Lithium has the highest specific heat capacity of any solid element.