Lanthanum (La)

Lanthanum properties

Atomic number

57

Atomic mass

138.91 u

Category

Lanthanide

Group

—

Period

6

Block

f-block

State at room temp.

Solid

Electronegativity

1.1

Melting point

1,193 K (919.8 °C)

Boiling point

3,737 K (3,463.8 °C)

Density

6.162 g/cm³

Valence electrons

2

Common charges

+3

Oxidation states

+3

Atomic radius

240 pm

Ionization energy

5.577 eV

Electron affinity

0.5 eV

Radioactive

No, has stable isotopes

Discovered

1839

Lanthanum electron configuration

The electron configuration of Lanthanum (La) is [Xe] 5d1 6s2. Its 57 electrons are arranged in shells as 2, 8, 18, 18, 9, 2.

Protons, neutrons and electrons in Lanthanum

A neutral Lanthanum atom has 57 protons and 57 electrons. Most Lanthanum atoms have about 82 neutrons: the atomic mass rounded to 139, minus the atomic number 57.

Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass

How many valence electrons does Lanthanum have?

2

Lanthanum has 2 valence electrons in its outermost shell. As an f-block element, its 4f or 5f electrons can also take part in bonding.

See every element: Periodic table with valence electrons

Lanthanum orbital diagram

Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations

Molar mass of Lanthanum

138.91 g/mol

One mole of Lanthanum atoms (6.022 × 10²³ atoms) has a mass of 138.91 grams. Use this value to convert between grams and moles.

Lanthanum facts

• Lanthanum gives its name to the lanthanides, the row of 15 elements from lanthanum to lutetium.
• Despite being called a rare earth metal, lanthanum is more abundant in Earth's crust than lead.
• Lanthanum (La) has atomic number 57 and is a solid at room temperature. It was discovered in 1839.

Position in the periodic table

Lanthanum is element 57, in period 6 of the periodic table. It is one of the Lanthanides in the f-block, shown in the rows below the main table.

All lanthanides

Uses of Lanthanum

Lanthanum's biggest use is in catalysts that crack crude oil into gasoline and other fuels. Lanthanum oxide makes high-quality optical glass for camera and telescope lenses, and a lanthanum–nickel alloy is used in nickel–metal hydride batteries, including those in many hybrid cars. Lanthanum carbonate is a medicine that helps people with kidney disease control the phosphate levels in their blood.

Who discovered Lanthanum?

Swedish chemist Carl Gustaf Mosander discovered lanthanum in 1839 in Stockholm, when he found a new oxide hidden in a sample of cerium nitrate. He named it from the Greek lanthanein, meaning 'to lie hidden'.

Where does the name come from?

Lanthanum comes from the Greek lanthanein, meaning 'to lie hidden'. Carl Gustaf Mosander chose the name in 1839 because the element had been hiding in cerium compounds, unnoticed by earlier chemists.

Discovery timeline